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	$226.53	12.425%	$254.6764	$254.68	$254.70	$254.70
Purchase #2	$6.56	11.526%	$7.3161	$7.32	$7.30	$7.30
Purchase #3	$80.67	9.482%	$88.3191	$88.32	$88.30	$88.30
Purchase #4	$240.88	6.282%	$256.0121	$256.01	$256.00	$256.00
Purchase #5	$40.38	13.598%	$45.8709	$45.87	$45.85	$45.90
Purchase #6	$190.96	11.631%	$213.1706	$213.17	$213.15	$213.20
Purchase #7	$144.89	8.634%	$157.3998	$157.40	$157.40	$157.40
7 purchase totals =	$930.87		$1,022.7650	$1,022.77	$1,022.70	$1,022.80