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	$49.78	7.436%	$53.4816	$53.48	$53.50	$53.50
Purchase #2	$190.34	3.109%	$196.2577	$196.26	$196.25	$196.30
Purchase #3	$36.31	9.785%	$39.8629	$39.86	$39.85	$39.90
Purchase #4	$153.25	5.233%	$161.2696	$161.27	$161.25	$161.30
Purchase #5	$209.48	12.817%	$236.3291	$236.33	$236.35	$236.30
Purchase #6	$19.83	13.332%	$22.4737	$22.47	$22.45	$22.50
Purchase #7	$59.28	9.643%	$64.9964	$65.00	$65.00	$65.00
7 purchase totals =	$718.27		$774.6710	$774.67	$774.65	$774.80