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	$199.92	10.125%	$220.1619	$220.16	$220.15	$220.20
Purchase #2	$42.70	13.658%	$48.532	$48.53	$48.55	$48.50
Purchase #3	$90.49	6.673%	$96.5284	$96.53	$96.55	$96.50
Purchase #4	$32.89	6.753%	$35.1111	$35.11	$35.10	$35.10
Purchase #5	$223.43	3.308%	$230.8211	$230.82	$230.80	$230.80
Purchase #6	$51.83	3.671%	$53.7327	$53.73	$53.75	$53.70
Purchase #7	$26.62	10.736%	$29.4779	$29.48	$29.50	$29.50
7 purchase totals =	$667.88		$714.3651	$714.36	$714.40	$714.30