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	$144.59	5.203%	$152.113	$152.11	$152.10	$152.10
Purchase #2	$227.29	12.421%	$255.5217	$255.52	$255.50	$255.50
Purchase #3	$145.35	10.420%	$160.4955	$160.50	$160.50	$160.50
Purchase #4	$146.28	13.353%	$165.8128	$165.81	$165.80	$165.80
Purchase #5	$118.71	3.319%	$122.65	$122.65	$122.65	$122.70
Purchase #6	$22.72	10.655%	$25.1408	$25.14	$25.15	$25.10
Purchase #7	$246.88	9.508%	$270.3534	$270.35	$270.35	$270.40
7 purchase totals =	$1,051.82		$1,152.0872	$1,152.08	$1,152.05	$1,152.10