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	$231.98	11.335%	$258.2749	$258.27	$258.25	$258.30
Purchase #2	$92.86	11.418%	$103.4628	$103.46	$103.45	$103.50
Purchase #3	$120.31	5.475%	$126.897	$126.90	$126.90	$126.90
Purchase #4	$126.56	4.195%	$131.8692	$131.87	$131.85	$131.90
Purchase #5	$122.93	4.619%	$128.6081	$128.61	$128.60	$128.60
Purchase #6	$87.58	6.850%	$93.5792	$93.58	$93.60	$93.60
Purchase #7	$168.46	6.485%	$179.3846	$179.38	$179.40	$179.40
7 purchase totals =	$950.68		$1,022.0758	$1,022.07	$1,022.05	$1,022.20