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	$212.38	3.598%	$220.0214	$220.02	$220.00	$220.00
Purchase #2	$243.82	12.425%	$274.1146	$274.11	$274.10	$274.10
Purchase #3	$109.38	6.574%	$116.5706	$116.57	$116.55	$116.60
Purchase #4	$90.72	4.431%	$94.7398	$94.74	$94.75	$94.70
Purchase #5	$159.79	7.684%	$172.0683	$172.07	$172.05	$172.10
Purchase #6	$200.96	9.262%	$219.5729	$219.57	$219.55	$219.60
Purchase #7	$168.89	11.843%	$188.8916	$188.89	$188.90	$188.90
7 purchase totals =	$1,185.94		$1,285.9792	$1,285.97	$1,285.90	$1,286.00