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	$239.57	12.496%	$269.5067	$269.51	$269.50	$269.50
Purchase #2	$130.95	5.658%	$138.3592	$138.36	$138.35	$138.40
Purchase #3	$182.98	7.211%	$196.1747	$196.17	$196.15	$196.20
Purchase #4	$46.86	10.403%	$51.7348	$51.73	$51.75	$51.70
Purchase #5	$153.71	11.733%	$171.7448	$171.74	$171.75	$171.70
Purchase #6	$59.29	3.497%	$61.3634	$61.36	$61.35	$61.40
Purchase #7	$35.39	5.198%	$37.2296	$37.23	$37.25	$37.20
7 purchase totals =	$848.75		$926.1132	$926.10	$926.10	$926.10