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	$101.91	12.419%	$114.5662	$114.57	$114.55	$114.60
Purchase #2	$50.69	11.337%	$56.4367	$56.44	$56.45	$56.40
Purchase #3	$11.45	8.635%	$12.4387	$12.44	$12.45	$12.40
Purchase #4	$203.67	4.365%	$212.5602	$212.56	$212.55	$212.60
Purchase #5	$78.64	13.431%	$89.2021	$89.20	$89.20	$89.20
Purchase #6	$98.36	4.840%	$103.1206	$103.12	$103.10	$103.10
Purchase #7	$70.55	11.177%	$78.4354	$78.44	$78.45	$78.40
7 purchase totals =	$615.27		$666.7599	$666.77	$666.75	$666.70