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	$228.64	10.692%	$253.0862	$253.09	$253.10	$253.10
Purchase #2	$88.56	12.382%	$99.5255	$99.53	$99.55	$99.50
Purchase #3	$133.89	9.778%	$146.9818	$146.98	$147.00	$147.00
Purchase #4	$209.58	3.323%	$216.5443	$216.54	$216.55	$216.50
Purchase #5	$25.26	11.469%	$28.1571	$28.16	$28.15	$28.20
Purchase #6	$118.25	10.477%	$130.6391	$130.64	$130.65	$130.60
Purchase #7	$29.31	10.287%	$32.3251	$32.33	$32.35	$32.30
7 purchase totals =	$833.49		$907.2591	$907.27	$907.35	$907.20