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	$215.71	5.184%	$226.8924	$226.89	$226.90	$226.90
Purchase #2	$38.88	7.335%	$41.7318	$41.73	$41.75	$41.70
Purchase #3	$172.58	13.679%	$196.1872	$196.19	$196.20	$196.20
Purchase #4	$200.27	4.269%	$208.8195	$208.82	$208.80	$208.80
Purchase #5	$158.82	10.433%	$175.3897	$175.39	$175.40	$175.40
Purchase #6	$105.63	8.139%	$114.2272	$114.23	$114.25	$114.20
Purchase #7	$28.65	11.207%	$31.8608	$31.86	$31.85	$31.90
7 purchase totals =	$920.54		$995.1086	$995.11	$995.15	$995.10