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	$176.46	7.651%	$189.961	$189.96	$189.95	$190.00
Purchase #2	$54.81	8.434%	$59.4327	$59.43	$59.45	$59.40
Purchase #3	$22.26	10.363%	$24.5668	$24.57	$24.55	$24.60
Purchase #4	$115.79	10.108%	$127.4941	$127.49	$127.50	$127.50
Purchase #5	$40.47	10.506%	$44.7218	$44.72	$44.70	$44.70
Purchase #6	$100.78	10.188%	$111.0475	$111.05	$111.05	$111.00
Purchase #7	$36.96	4.775%	$38.7248	$38.72	$38.70	$38.70
7 purchase totals =	$547.53		$595.9487	$595.94	$595.90	$595.90