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	$212.98	12.204%	$238.9721	$238.97	$238.95	$239.00
Purchase #2	$11.38	13.200%	$12.8822	$12.88	$12.90	$12.90
Purchase #3	$71.51	4.671%	$74.8502	$74.85	$74.85	$74.90
Purchase #4	$12.34	11.866%	$13.8043	$13.80	$13.80	$13.80
Purchase #5	$65.76	8.163%	$71.128	$71.13	$71.15	$71.10
Purchase #6	$35.64	4.516%	$37.2495	$37.25	$37.25	$37.20
Purchase #7	$93.68	10.311%	$103.3393	$103.34	$103.35	$103.30
7 purchase totals =	$503.29		$552.2256	$552.22	$552.25	$552.20