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	$203.39	9.391%	$222.4904	$222.49	$222.50	$222.50
Purchase #2	$195.63	13.817%	$222.6602	$222.66	$222.65	$222.70
Purchase #3	$176.99	6.300%	$188.1404	$188.14	$188.15	$188.10
Purchase #4	$155.46	12.717%	$175.2298	$175.23	$175.25	$175.20
Purchase #5	$170.38	7.693%	$183.4873	$183.49	$183.50	$183.50
Purchase #6	$78.94	11.605%	$88.101	$88.10	$88.10	$88.10
Purchase #7	$31.72	5.838%	$33.5718	$33.57	$33.55	$33.60
7 purchase totals =	$1,012.51		$1,113.6809	$1,113.68	$1,113.70	$1,113.70