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	$224.93	8.332%	$243.6712	$243.67	$243.65	$243.70
Purchase #2	$9.51	7.461%	$10.2195	$10.22	$10.20	$10.20
Purchase #3	$19.59	5.761%	$20.7186	$20.72	$20.70	$20.70
Purchase #4	$188.56	11.307%	$209.8805	$209.88	$209.90	$209.90
Purchase #5	$111.59	4.690%	$116.8236	$116.82	$116.80	$116.80
Purchase #6	$245.39	12.389%	$275.7914	$275.79	$275.80	$275.80
Purchase #7	$224.46	8.428%	$243.3775	$243.38	$243.40	$243.40
7 purchase totals =	$1,024.03		$1,120.4823	$1,120.48	$1,120.45	$1,120.50