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	$229.86	7.681%	$247.5155	$247.52	$247.50	$247.50
Purchase #2	$22.44	8.241%	$24.2893	$24.29	$24.30	$24.30
Purchase #3	$32.84	5.309%	$34.5835	$34.58	$34.60	$34.60
Purchase #4	$241.50	10.832%	$267.6593	$267.66	$267.65	$267.70
Purchase #5	$75.49	3.679%	$78.2673	$78.27	$78.25	$78.30
Purchase #6	$123.89	3.127%	$127.764	$127.76	$127.75	$127.80
Purchase #7	$85.76	3.368%	$88.6484	$88.65	$88.65	$88.60
7 purchase totals =	$811.78		$868.7273	$868.73	$868.70	$868.80