Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$213.29	4.587%	$223.0736	$223.07	$223.05	$223.10
Purchase #2	$114.37	12.369%	$128.5164	$128.52	$128.50	$128.50
Purchase #3	$222.94	7.536%	$239.7408	$239.74	$239.75	$239.70
Purchase #4	$81.43	6.480%	$86.7067	$86.71	$86.70	$86.70
Purchase #5	$104.44	6.736%	$111.4751	$111.48	$111.50	$111.50
Purchase #6	$38.71	7.327%	$41.5463	$41.55	$41.55	$41.50
Purchase #7	$51.42	9.141%	$56.1203	$56.12	$56.10	$56.10
7 purchase totals =	$826.60		$887.1792	$887.19	$887.15	$887.10