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	$149.84	10.511%	$165.5897	$165.59	$165.60	$165.60
Purchase #2	$107.59	11.318%	$119.767	$119.77	$119.75	$119.80
Purchase #3	$83.29	7.800%	$89.7866	$89.79	$89.80	$89.80
Purchase #4	$92.82	8.614%	$100.8155	$100.82	$100.80	$100.80
Purchase #5	$223.72	12.398%	$251.4568	$251.46	$251.45	$251.50
Purchase #6	$244.73	8.333%	$265.1234	$265.12	$265.10	$265.10
Purchase #7	$55.80	8.680%	$60.6434	$60.64	$60.65	$60.60
7 purchase totals =	$957.79		$1,053.1824	$1,053.19	$1,053.15	$1,053.20