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	$148.87	7.208%	$159.6005	$159.60	$159.60	$159.60
Purchase #2	$198.75	8.632%	$215.9061	$215.91	$215.90	$215.90
Purchase #3	$208.49	8.157%	$225.4965	$225.50	$225.50	$225.50
Purchase #4	$204.89	4.589%	$214.2924	$214.29	$214.30	$214.30
Purchase #5	$123.72	5.335%	$130.3205	$130.32	$130.30	$130.30
Purchase #6	$13.53	7.809%	$14.5866	$14.59	$14.60	$14.60
Purchase #7	$207.62	13.825%	$236.3235	$236.32	$236.30	$236.30
7 purchase totals =	$1,105.87		$1,196.5261	$1,196.53	$1,196.50	$1,196.50