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	$234.65	7.467%	$252.1713	$252.17	$252.15	$252.20
Purchase #2	$220.41	9.717%	$241.8272	$241.83	$241.85	$241.80
Purchase #3	$40.53	5.766%	$42.867	$42.87	$42.85	$42.90
Purchase #4	$159.97	12.508%	$179.979	$179.98	$180.00	$180.00
Purchase #5	$213.55	11.218%	$237.506	$237.51	$237.50	$237.50
Purchase #6	$69.27	4.700%	$72.5257	$72.53	$72.55	$72.50
Purchase #7	$139.69	5.116%	$146.8365	$146.84	$146.85	$146.80
7 purchase totals =	$1,078.07		$1,173.7127	$1,173.73	$1,173.75	$1,173.70