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	$146.97	3.803%	$152.5593	$152.56	$152.55	$152.60
Purchase #2	$104.53	6.539%	$111.3652	$111.37	$111.35	$111.40
Purchase #3	$133.57	5.592%	$141.0392	$141.04	$141.05	$141.00
Purchase #4	$104.55	11.260%	$116.3223	$116.32	$116.30	$116.30
Purchase #5	$226.44	12.829%	$255.49	$255.49	$255.50	$255.50
Purchase #6	$244.55	3.220%	$252.4245	$252.42	$252.40	$252.40
Purchase #7	$139.57	6.503%	$148.6462	$148.65	$148.65	$148.60
7 purchase totals =	$1,100.18		$1,177.8467	$1,177.85	$1,177.80	$1,177.80