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	$218.72	11.683%	$244.2731	$244.27	$244.25	$244.30
Purchase #2	$205.83	12.315%	$231.178	$231.18	$231.20	$231.20
Purchase #3	$208.63	10.566%	$230.6738	$230.67	$230.65	$230.70
Purchase #4	$85.96	5.747%	$90.9001	$90.90	$90.90	$90.90
Purchase #5	$100.35	10.811%	$111.1988	$111.20	$111.20	$111.20
Purchase #6	$140.26	11.321%	$156.1388	$156.14	$156.15	$156.10
Purchase #7	$170.58	11.685%	$190.5123	$190.51	$190.50	$190.50
7 purchase totals =	$1,130.33		$1,254.8749	$1,254.87	$1,254.85	$1,254.90