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	$105.45	8.433%	$114.3426	$114.34	$114.35	$114.30
Purchase #2	$55.94	5.460%	$58.9943	$58.99	$59.00	$59.00
Purchase #3	$99.67	5.849%	$105.4997	$105.50	$105.50	$105.50
Purchase #4	$37.81	5.268%	$39.8018	$39.80	$39.80	$39.80
Purchase #5	$221.32	10.424%	$244.3904	$244.39	$244.40	$244.40
Purchase #6	$117.68	11.464%	$131.1708	$131.17	$131.15	$131.20
Purchase #7	$165.76	7.575%	$178.3163	$178.32	$178.30	$178.30
7 purchase totals =	$803.63		$872.5159	$872.51	$872.50	$872.50