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	$164.45	10.556%	$181.8093	$181.81	$181.80	$181.80
Purchase #2	$10.89	11.234%	$12.1134	$12.11	$12.10	$12.10
Purchase #3	$244.86	6.485%	$260.7392	$260.74	$260.75	$260.70
Purchase #4	$89.81	6.146%	$95.3297	$95.33	$95.35	$95.30
Purchase #5	$103.45	8.467%	$112.2091	$112.21	$112.20	$112.20
Purchase #6	$54.70	8.853%	$59.5426	$59.54	$59.55	$59.50
Purchase #7	$202.37	11.129%	$224.8918	$224.89	$224.90	$224.90
7 purchase totals =	$870.53		$946.6351	$946.63	$946.65	$946.50