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	$106.87	10.449%	$118.0368	$118.04	$118.05	$118.00
Purchase #2	$247.27	6.485%	$263.3055	$263.31	$263.30	$263.30
Purchase #3	$153.55	5.144%	$161.4486	$161.45	$161.45	$161.40
Purchase #4	$189.27	6.148%	$200.9063	$200.91	$200.90	$200.90
Purchase #5	$205.69	11.871%	$230.1075	$230.11	$230.10	$230.10
Purchase #6	$6.90	8.447%	$7.4828	$7.48	$7.50	$7.50
Purchase #7	$137.89	10.325%	$152.1271	$152.13	$152.15	$152.10
7 purchase totals =	$1,047.44		$1,133.4146	$1,133.43	$1,133.45	$1,133.30