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	$182.84	9.110%	$199.4967	$199.50	$199.50	$199.50
Purchase #2	$13.40	11.182%	$14.8984	$14.90	$14.90	$14.90
Purchase #3	$56.42	5.530%	$59.54	$59.54	$59.55	$59.50
Purchase #4	$152.40	12.307%	$171.1559	$171.16	$171.15	$171.20
Purchase #5	$114.93	13.411%	$130.3433	$130.34	$130.35	$130.30
Purchase #6	$96.93	8.474%	$105.1438	$105.14	$105.15	$105.10
Purchase #7	$36.60	11.118%	$40.6692	$40.67	$40.65	$40.70
7 purchase totals =	$653.52		$721.2473	$721.25	$721.25	$721.20