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	$77.37	10.618%	$85.5851	$85.59	$85.60	$85.60
Purchase #2	$152.77	12.838%	$172.3826	$172.38	$172.40	$172.40
Purchase #3	$230.29	13.526%	$261.439	$261.44	$261.45	$261.40
Purchase #4	$36.80	4.467%	$38.4439	$38.44	$38.45	$38.40
Purchase #5	$23.77	12.201%	$26.6702	$26.67	$26.65	$26.70
Purchase #6	$55.37	11.109%	$61.5211	$61.52	$61.50	$61.50
Purchase #7	$84.97	6.730%	$90.6885	$90.69	$90.70	$90.70
7 purchase totals =	$661.34		$736.7304	$736.73	$736.75	$736.70