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	$135.64	7.680%	$146.0572	$146.06	$146.05	$146.10
Purchase #2	$61.28	7.596%	$65.9348	$65.93	$65.95	$65.90
Purchase #3	$134.48	6.266%	$142.9065	$142.91	$142.90	$142.90
Purchase #4	$138.76	10.382%	$153.1661	$153.17	$153.15	$153.20
Purchase #5	$99.54	6.419%	$105.9295	$105.93	$105.95	$105.90
Purchase #6	$223.81	8.503%	$242.8406	$242.84	$242.85	$242.80
Purchase #7	$58.31	10.269%	$64.2979	$64.30	$64.30	$64.30
7 purchase totals =	$851.82		$921.1326	$921.14	$921.15	$921.10