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	$164.51	12.390%	$184.8928	$184.89	$184.90	$184.90
Purchase #2	$138.81	11.807%	$155.1993	$155.20	$155.20	$155.20
Purchase #3	$148.48	11.299%	$165.2568	$165.26	$165.25	$165.30
Purchase #4	$76.92	3.570%	$79.666	$79.67	$79.65	$79.70
Purchase #5	$46.35	13.862%	$52.775	$52.78	$52.80	$52.80
Purchase #6	$186.40	13.439%	$211.4503	$211.45	$211.45	$211.50
Purchase #7	$225.33	13.841%	$256.5179	$256.52	$256.50	$256.50
7 purchase totals =	$986.80		$1,105.7581	$1,105.77	$1,105.75	$1,105.90