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	$244.89	4.826%	$256.7084	$256.71	$256.70	$256.70
Purchase #2	$245.50	7.458%	$263.8094	$263.81	$263.80	$263.80
Purchase #3	$179.28	3.362%	$185.3074	$185.31	$185.30	$185.30
Purchase #4	$250.39	11.766%	$279.8509	$279.85	$279.85	$279.90
Purchase #5	$71.58	7.538%	$76.9757	$76.98	$77.00	$77.00
Purchase #6	$88.53	8.848%	$96.3631	$96.36	$96.35	$96.40
Purchase #7	$111.55	10.184%	$122.9103	$122.91	$122.90	$122.90
7 purchase totals =	$1,191.72		$1,281.9252	$1,281.93	$1,281.90	$1,282.00