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	$100.46	10.496%	$111.0043	$111.00	$111.00	$111.00
Purchase #2	$126.67	13.561%	$143.8477	$143.85	$143.85	$143.80
Purchase #3	$54.97	11.668%	$61.3839	$61.38	$61.40	$61.40
Purchase #4	$214.56	6.869%	$229.2981	$229.30	$229.30	$229.30
Purchase #5	$223.45	12.199%	$250.7087	$250.71	$250.70	$250.70
Purchase #6	$203.60	10.311%	$224.5932	$224.59	$224.60	$224.60
Purchase #7	$73.88	13.275%	$83.6876	$83.69	$83.70	$83.70
7 purchase totals =	$997.59		$1,104.5235	$1,104.52	$1,104.55	$1,104.50