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	$232.93	9.229%	$254.4271	$254.43	$254.45	$254.40
Purchase #2	$38.86	3.105%	$40.0666	$40.07	$40.05	$40.10
Purchase #3	$215.34	6.497%	$229.3306	$229.33	$229.35	$229.30
Purchase #4	$71.45	10.133%	$78.69	$78.69	$78.70	$78.70
Purchase #5	$139.72	5.180%	$146.9575	$146.96	$146.95	$147.00
Purchase #6	$214.74	4.272%	$223.9137	$223.91	$223.90	$223.90
Purchase #7	$36.83	11.601%	$41.1026	$41.10	$41.10	$41.10
7 purchase totals =	$949.87		$1,014.4881	$1,014.49	$1,014.50	$1,014.50