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	$82.31	8.353%	$89.1854	$89.19	$89.20	$89.20
Purchase #2	$196.62	7.656%	$211.6732	$211.67	$211.65	$211.70
Purchase #3	$185.98	7.273%	$199.5063	$199.51	$199.50	$199.50
Purchase #4	$60.71	10.693%	$67.2017	$67.20	$67.20	$67.20
Purchase #5	$78.55	10.408%	$86.7255	$86.73	$86.75	$86.70
Purchase #6	$151.55	5.210%	$159.4458	$159.45	$159.45	$159.40
Purchase #7	$57.33	3.255%	$59.1961	$59.20	$59.20	$59.20
7 purchase totals =	$813.05		$872.9340	$872.95	$872.95	$872.90