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	$135.43	12.749%	$152.696	$152.70	$152.70	$152.70
Purchase #2	$156.28	10.258%	$172.3112	$172.31	$172.30	$172.30
Purchase #3	$57.54	3.726%	$59.6839	$59.68	$59.70	$59.70
Purchase #4	$38.92	8.201%	$42.1118	$42.11	$42.10	$42.10
Purchase #5	$79.37	7.379%	$85.2267	$85.23	$85.25	$85.20
Purchase #6	$141.34	8.741%	$153.6945	$153.69	$153.70	$153.70
Purchase #7	$237.61	5.552%	$250.8021	$250.80	$250.80	$250.80
7 purchase totals =	$846.49		$916.5262	$916.52	$916.55	$916.50