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	$239.49	5.738%	$253.2319	$253.23	$253.25	$253.20
Purchase #2	$10.82	11.821%	$12.099	$12.10	$12.10	$12.10
Purchase #3	$70.84	9.416%	$77.5103	$77.51	$77.50	$77.50
Purchase #4	$132.90	4.494%	$138.8725	$138.87	$138.85	$138.90
Purchase #5	$209.49	9.262%	$228.893	$228.89	$228.90	$228.90
Purchase #6	$105.57	4.707%	$110.5392	$110.54	$110.55	$110.50
Purchase #7	$242.39	12.700%	$273.1735	$273.17	$273.15	$273.20
7 purchase totals =	$1,011.50		$1,094.3194	$1,094.31	$1,094.30	$1,094.30