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	$35.69	3.596%	$36.9734	$36.97	$36.95	$37.00
Purchase #2	$111.89	13.632%	$127.1428	$127.14	$127.15	$127.10
Purchase #3	$212.97	12.467%	$239.521	$239.52	$239.50	$239.50
Purchase #4	$60.80	6.694%	$64.87	$64.87	$64.85	$64.90
Purchase #5	$116.33	9.664%	$127.5721	$127.57	$127.55	$127.60
Purchase #6	$41.27	8.271%	$44.6834	$44.68	$44.70	$44.70
Purchase #7	$31.58	4.733%	$33.0747	$33.07	$33.05	$33.10
7 purchase totals =	$610.53		$673.8374	$673.82	$673.75	$673.90