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	$175.43	3.484%	$181.542	$181.54	$181.55	$181.50
Purchase #2	$90.40	9.244%	$98.7566	$98.76	$98.75	$98.80
Purchase #3	$136.90	3.491%	$141.6792	$141.68	$141.70	$141.70
Purchase #4	$91.25	4.810%	$95.6391	$95.64	$95.65	$95.60
Purchase #5	$104.89	6.234%	$111.4288	$111.43	$111.45	$111.40
Purchase #6	$104.67	13.344%	$118.6372	$118.64	$118.65	$118.60
Purchase #7	$138.99	9.738%	$152.5248	$152.52	$152.50	$152.50
7 purchase totals =	$842.53		$900.2077	$900.21	$900.25	$900.10