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	$217.94	13.165%	$246.6318	$246.63	$246.65	$246.60
Purchase #2	$30.44	11.152%	$33.8347	$33.83	$33.85	$33.80
Purchase #3	$239.73	13.645%	$272.4412	$272.44	$272.45	$272.40
Purchase #4	$235.66	12.329%	$264.7145	$264.71	$264.70	$264.70
Purchase #5	$174.92	9.438%	$191.4289	$191.43	$191.45	$191.40
Purchase #6	$111.71	4.587%	$116.8341	$116.83	$116.85	$116.80
Purchase #7	$200.96	10.732%	$222.527	$222.53	$222.55	$222.50
7 purchase totals =	$1,211.36		$1,348.4122	$1,348.40	$1,348.50	$1,348.20