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	$37.88	9.104%	$41.3286	$41.33	$41.35	$41.30
Purchase #2	$138.58	12.214%	$155.5062	$155.51	$155.50	$155.50
Purchase #3	$100.78	4.562%	$105.3776	$105.38	$105.40	$105.40
Purchase #4	$225.78	9.502%	$247.2336	$247.23	$247.25	$247.20
Purchase #5	$203.25	6.340%	$216.1361	$216.14	$216.15	$216.10
Purchase #6	$106.38	9.349%	$116.3255	$116.33	$116.35	$116.30
Purchase #7	$158.41	10.175%	$174.5282	$174.53	$174.55	$174.50
7 purchase totals =	$971.06		$1,056.4358	$1,056.45	$1,056.55	$1,056.30