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	$45.43	11.496%	$50.6526	$50.65	$50.65	$50.70
Purchase #2	$225.53	13.715%	$256.4614	$256.46	$256.45	$256.50
Purchase #3	$180.79	9.446%	$197.8674	$197.87	$197.85	$197.90
Purchase #4	$222.94	10.303%	$245.9095	$245.91	$245.90	$245.90
Purchase #5	$182.41	7.741%	$196.5304	$196.53	$196.55	$196.50
Purchase #6	$54.46	3.605%	$56.4233	$56.42	$56.40	$56.40
Purchase #7	$46.90	10.175%	$51.6721	$51.67	$51.65	$51.70
7 purchase totals =	$958.46		$1,055.5167	$1,055.51	$1,055.45	$1,055.60