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	$53.83	11.141%	$59.8272	$59.83	$59.85	$59.80
Purchase #2	$34.49	12.223%	$38.7057	$38.71	$38.70	$38.70
Purchase #3	$83.26	13.102%	$94.1687	$94.17	$94.15	$94.20
Purchase #4	$100.55	4.665%	$105.2407	$105.24	$105.25	$105.20
Purchase #5	$90.85	3.794%	$94.2968	$94.30	$94.30	$94.30
Purchase #6	$108.49	13.533%	$123.172	$123.17	$123.15	$123.20
Purchase #7	$225.87	11.375%	$251.5627	$251.56	$251.55	$251.60
7 purchase totals =	$697.34		$766.9738	$766.98	$766.95	$767.00