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	$106.68	11.275%	$118.7082	$118.71	$118.70	$118.70
Purchase #2	$220.71	9.743%	$242.2138	$242.21	$242.20	$242.20
Purchase #3	$42.68	9.121%	$46.5728	$46.57	$46.55	$46.60
Purchase #4	$214.71	13.290%	$243.245	$243.25	$243.25	$243.20
Purchase #5	$83.89	7.169%	$89.9041	$89.90	$89.90	$89.90
Purchase #6	$110.38	12.400%	$124.0671	$124.07	$124.05	$124.10
Purchase #7	$196.98	13.180%	$222.942	$222.94	$222.95	$222.90
7 purchase totals =	$976.03		$1,087.6530	$1,087.65	$1,087.60	$1,087.60