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	$114.78	8.873%	$124.9644	$124.96	$124.95	$125.00
Purchase #2	$141.94	4.474%	$148.2904	$148.29	$148.30	$148.30
Purchase #3	$239.80	6.548%	$255.5021	$255.50	$255.50	$255.50
Purchase #4	$141.50	6.439%	$150.6112	$150.61	$150.60	$150.60
Purchase #5	$230.91	11.443%	$257.333	$257.33	$257.35	$257.30
Purchase #6	$76.71	11.572%	$85.5869	$85.59	$85.60	$85.60
Purchase #7	$239.75	11.755%	$267.9326	$267.93	$267.95	$267.90
7 purchase totals =	$1,185.39		$1,290.2206	$1,290.21	$1,290.25	$1,290.20