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	$237.43	11.501%	$264.7368	$264.74	$264.75	$264.70
Purchase #2	$225.89	13.234%	$255.7843	$255.78	$255.80	$255.80
Purchase #3	$213.70	11.640%	$238.5747	$238.57	$238.55	$238.60
Purchase #4	$237.44	13.545%	$269.6012	$269.60	$269.60	$269.60
Purchase #5	$26.82	4.726%	$28.0875	$28.09	$28.10	$28.10
Purchase #6	$211.88	5.694%	$223.9444	$223.94	$223.95	$223.90
Purchase #7	$83.95	5.285%	$88.3868	$88.39	$88.40	$88.40
7 purchase totals =	$1,237.11		$1,369.1157	$1,369.11	$1,369.15	$1,369.10