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	$35.30	5.741%	$37.3266	$37.33	$37.35	$37.30
Purchase #2	$244.36	7.575%	$262.8703	$262.87	$262.85	$262.90
Purchase #3	$155.48	7.175%	$166.6357	$166.64	$166.65	$166.60
Purchase #4	$122.50	4.387%	$127.8741	$127.87	$127.85	$127.90
Purchase #5	$90.80	4.412%	$94.8061	$94.81	$94.80	$94.80
Purchase #6	$50.44	11.496%	$56.2386	$56.24	$56.25	$56.20
Purchase #7	$237.54	8.119%	$256.8259	$256.83	$256.85	$256.80
7 purchase totals =	$936.42		$1,002.5773	$1,002.59	$1,002.60	$1,002.50