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	$141.45	3.743%	$146.7445	$146.74	$146.75	$146.70
Purchase #2	$72.73	5.783%	$76.936	$76.94	$76.95	$76.90
Purchase #3	$223.56	10.265%	$246.5084	$246.51	$246.50	$246.50
Purchase #4	$144.80	6.522%	$154.2439	$154.24	$154.25	$154.20
Purchase #5	$225.81	7.293%	$242.2783	$242.28	$242.30	$242.30
Purchase #6	$187.99	11.647%	$209.8852	$209.89	$209.90	$209.90
Purchase #7	$80.82	10.536%	$89.3352	$89.34	$89.35	$89.30
7 purchase totals =	$1,077.16		$1,165.9315	$1,165.94	$1,166.00	$1,165.80