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	$181.79	4.712%	$190.3559	$190.36	$190.35	$190.40
Purchase #2	$208.59	12.830%	$235.3521	$235.35	$235.35	$235.40
Purchase #3	$207.33	7.612%	$223.112	$223.11	$223.10	$223.10
Purchase #4	$150.87	6.267%	$160.325	$160.33	$160.35	$160.30
Purchase #5	$117.92	5.560%	$124.4764	$124.48	$124.50	$124.50
Purchase #6	$227.59	13.741%	$258.8631	$258.86	$258.85	$258.90
Purchase #7	$242.39	3.316%	$250.4277	$250.43	$250.45	$250.40
7 purchase totals =	$1,336.48		$1,442.9122	$1,442.92	$1,442.95	$1,443.00