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	$185.67	9.603%	$203.4999	$203.50	$203.50	$203.50
Purchase #2	$96.36	4.143%	$100.3522	$100.35	$100.35	$100.40
Purchase #3	$39.64	3.348%	$40.9671	$40.97	$40.95	$41.00
Purchase #4	$87.85	10.635%	$97.1928	$97.19	$97.20	$97.20
Purchase #5	$106.41	4.760%	$111.4751	$111.48	$111.50	$111.50
Purchase #6	$85.85	12.174%	$96.3014	$96.30	$96.30	$96.30
Purchase #7	$20.69	5.178%	$21.7613	$21.76	$21.75	$21.80
7 purchase totals =	$622.47		$671.5498	$671.55	$671.55	$671.70