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	$194.66	13.734%	$221.3946	$221.39	$221.40	$221.40
Purchase #2	$215.83	13.290%	$244.5138	$244.51	$244.50	$244.50
Purchase #3	$72.49	13.707%	$82.4262	$82.43	$82.45	$82.40
Purchase #4	$87.44	7.842%	$94.297	$94.30	$94.30	$94.30
Purchase #5	$173.47	12.587%	$195.3047	$195.30	$195.30	$195.30
Purchase #6	$121.47	5.156%	$127.733	$127.73	$127.75	$127.70
Purchase #7	$34.76	7.400%	$37.3322	$37.33	$37.35	$37.30
7 purchase totals =	$900.12		$1,003.0015	$1,002.99	$1,003.05	$1,002.90