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	$184.50	11.485%	$205.6898	$205.69	$205.70	$205.70
Purchase #2	$16.98	10.508%	$18.7643	$18.76	$18.75	$18.80
Purchase #3	$161.64	9.587%	$177.1364	$177.14	$177.15	$177.10
Purchase #4	$77.72	6.863%	$83.0539	$83.05	$83.05	$83.10
Purchase #5	$99.71	11.472%	$111.1487	$111.15	$111.15	$111.10
Purchase #6	$173.61	5.303%	$182.8165	$182.82	$182.80	$182.80
Purchase #7	$67.96	6.543%	$72.4066	$72.41	$72.40	$72.40
7 purchase totals =	$782.12		$851.0162	$851.02	$851.00	$851.00