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	$196.52	12.281%	$220.6546	$220.65	$220.65	$220.70
Purchase #2	$181.34	12.243%	$203.5415	$203.54	$203.55	$203.50
Purchase #3	$33.63	10.570%	$37.1847	$37.18	$37.20	$37.20
Purchase #4	$29.59	9.867%	$32.5096	$32.51	$32.50	$32.50
Purchase #5	$200.34	11.536%	$223.4512	$223.45	$223.45	$223.50
Purchase #6	$126.32	10.113%	$139.0947	$139.09	$139.10	$139.10
Purchase #7	$131.61	12.255%	$147.7388	$147.74	$147.75	$147.70
7 purchase totals =	$899.35		$1,004.1751	$1,004.16	$1,004.20	$1,004.20