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	$152.92	3.311%	$157.9832	$157.98	$158.00	$158.00
Purchase #2	$29.68	12.867%	$33.4989	$33.50	$33.50	$33.50
Purchase #3	$62.60	13.598%	$71.1123	$71.11	$71.10	$71.10
Purchase #4	$141.52	6.263%	$150.3834	$150.38	$150.40	$150.40
Purchase #5	$211.53	8.204%	$228.8839	$228.88	$228.90	$228.90
Purchase #6	$38.75	5.250%	$40.7844	$40.78	$40.80	$40.80
Purchase #7	$221.82	13.501%	$251.7679	$251.77	$251.75	$251.80
7 purchase totals =	$858.82		$934.4140	$934.40	$934.45	$934.50