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	$41.70	13.307%	$47.249	$47.25	$47.25	$47.20
Purchase #2	$32.31	7.289%	$34.6651	$34.67	$34.65	$34.70
Purchase #3	$176.66	11.244%	$196.5237	$196.52	$196.50	$196.50
Purchase #4	$137.42	11.293%	$152.9388	$152.94	$152.95	$152.90
Purchase #5	$93.57	12.187%	$104.9734	$104.97	$104.95	$105.00
Purchase #6	$64.82	13.692%	$73.6952	$73.70	$73.70	$73.70
Purchase #7	$129.34	7.740%	$139.3509	$139.35	$139.35	$139.40
7 purchase totals =	$675.82		$749.3961	$749.40	$749.35	$749.40