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	$130.67	11.375%	$145.5337	$145.53	$145.55	$145.50
Purchase #2	$175.62	13.873%	$199.9838	$199.98	$200.00	$200.00
Purchase #3	$68.82	13.844%	$78.3474	$78.35	$78.35	$78.30
Purchase #4	$180.42	4.766%	$189.0188	$189.02	$189.00	$189.00
Purchase #5	$148.54	7.248%	$159.3062	$159.31	$159.30	$159.30
Purchase #6	$93.62	6.645%	$99.841	$99.84	$99.85	$99.80
Purchase #7	$202.46	3.485%	$209.5157	$209.52	$209.50	$209.50
7 purchase totals =	$1,000.15		$1,081.5466	$1,081.55	$1,081.55	$1,081.40