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	$125.82	4.151%	$131.0428	$131.04	$131.05	$131.00
Purchase #2	$161.85	8.858%	$176.1867	$176.19	$176.20	$176.20
Purchase #3	$145.65	10.380%	$160.7685	$160.77	$160.75	$160.80
Purchase #4	$95.68	6.298%	$101.7059	$101.71	$101.70	$101.70
Purchase #5	$241.46	11.642%	$269.5708	$269.57	$269.55	$269.60
Purchase #6	$196.82	10.423%	$217.3345	$217.33	$217.35	$217.30
Purchase #7	$35.83	5.740%	$37.8866	$37.89	$37.90	$37.90
7 purchase totals =	$1,003.11		$1,094.4958	$1,094.50	$1,094.50	$1,094.50