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	$233.26	12.463%	$262.3312	$262.33	$262.35	$262.30
Purchase #2	$235.75	4.575%	$246.5356	$246.54	$246.55	$246.50
Purchase #3	$38.81	9.145%	$42.3592	$42.36	$42.35	$42.40
Purchase #4	$146.82	4.390%	$153.2654	$153.27	$153.25	$153.30
Purchase #5	$146.64	4.299%	$152.9441	$152.94	$152.95	$152.90
Purchase #6	$32.41	13.371%	$36.7435	$36.74	$36.75	$36.70
Purchase #7	$129.29	13.114%	$146.2451	$146.25	$146.25	$146.20
7 purchase totals =	$962.98		$1,040.4241	$1,040.43	$1,040.45	$1,040.30