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	$33.81	10.703%	$37.4287	$37.43	$37.45	$37.40
Purchase #2	$243.34	7.303%	$261.1111	$261.11	$261.10	$261.10
Purchase #3	$193.80	3.389%	$200.3679	$200.37	$200.35	$200.40
Purchase #4	$168.39	13.525%	$191.1647	$191.16	$191.15	$191.20
Purchase #5	$153.48	11.358%	$170.9123	$170.91	$170.90	$170.90
Purchase #6	$56.67	6.796%	$60.5213	$60.52	$60.50	$60.50
Purchase #7	$166.52	12.732%	$187.7213	$187.72	$187.70	$187.70
7 purchase totals =	$1,016.01		$1,109.2273	$1,109.22	$1,109.15	$1,109.20