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	$171.76	10.856%	$190.4063	$190.41	$190.40	$190.40
Purchase #2	$207.50	7.434%	$222.9256	$222.93	$222.95	$222.90
Purchase #3	$227.90	11.545%	$254.2111	$254.21	$254.20	$254.20
Purchase #4	$121.57	7.853%	$131.1169	$131.12	$131.10	$131.10
Purchase #5	$58.79	11.854%	$65.759	$65.76	$65.75	$65.80
Purchase #6	$54.40	12.136%	$61.002	$61.00	$61.00	$61.00
Purchase #7	$119.96	13.298%	$135.9123	$135.91	$135.90	$135.90
7 purchase totals =	$961.88		$1,061.3332	$1,061.34	$1,061.30	$1,061.30