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	$192.31	12.133%	$215.643	$215.64	$215.65	$215.60
Purchase #2	$238.65	10.725%	$264.2452	$264.25	$264.25	$264.20
Purchase #3	$149.85	10.411%	$165.4509	$165.45	$165.45	$165.50
Purchase #4	$131.74	9.317%	$144.0142	$144.01	$144.00	$144.00
Purchase #5	$181.37	12.185%	$203.4699	$203.47	$203.45	$203.50
Purchase #6	$13.49	7.568%	$14.5109	$14.51	$14.50	$14.50
Purchase #7	$118.89	11.729%	$132.8346	$132.83	$132.85	$132.80
7 purchase totals =	$1,026.30		$1,140.1687	$1,140.16	$1,140.15	$1,140.10