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	$151.39	13.291%	$171.5112	$171.51	$171.50	$171.50
Purchase #2	$147.84	5.433%	$155.8721	$155.87	$155.85	$155.90
Purchase #3	$85.99	10.824%	$95.2976	$95.30	$95.30	$95.30
Purchase #4	$119.43	9.188%	$130.4032	$130.40	$130.40	$130.40
Purchase #5	$52.75	12.576%	$59.3838	$59.38	$59.40	$59.40
Purchase #6	$204.96	3.408%	$211.945	$211.95	$211.95	$211.90
Purchase #7	$151.81	7.199%	$162.7388	$162.74	$162.75	$162.70
7 purchase totals =	$914.17		$987.1517	$987.15	$987.15	$987.10