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	$64.25	5.714%	$67.9212	$67.92	$67.90	$67.90
Purchase #2	$159.29	3.660%	$165.12	$165.12	$165.10	$165.10
Purchase #3	$195.64	5.503%	$206.4061	$206.41	$206.40	$206.40
Purchase #4	$82.86	11.527%	$92.4113	$92.41	$92.40	$92.40
Purchase #5	$148.81	6.679%	$158.749	$158.75	$158.75	$158.70
Purchase #6	$116.82	3.279%	$120.6505	$120.65	$120.65	$120.70
Purchase #7	$190.28	3.252%	$196.4679	$196.47	$196.45	$196.50
7 purchase totals =	$957.95		$1,007.7260	$1,007.73	$1,007.65	$1,007.70