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	$121.46	8.149%	$131.3578	$131.36	$131.35	$131.40
Purchase #2	$212.37	12.480%	$238.8738	$238.87	$238.85	$238.90
Purchase #3	$47.98	10.610%	$53.0707	$53.07	$53.05	$53.10
Purchase #4	$196.47	13.655%	$223.298	$223.30	$223.30	$223.30
Purchase #5	$33.70	11.813%	$37.681	$37.68	$37.70	$37.70
Purchase #6	$125.89	8.613%	$136.7329	$136.73	$136.75	$136.70
Purchase #7	$111.41	10.771%	$123.41	$123.41	$123.40	$123.40
7 purchase totals =	$849.28		$944.4242	$944.42	$944.40	$944.50