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	$45.79	3.421%	$47.3565	$47.36	$47.35	$47.40
Purchase #2	$35.95	12.579%	$40.4722	$40.47	$40.45	$40.50
Purchase #3	$221.77	7.445%	$238.2808	$238.28	$238.30	$238.30
Purchase #4	$93.41	4.384%	$97.5051	$97.51	$97.50	$97.50
Purchase #5	$57.33	7.551%	$61.659	$61.66	$61.65	$61.70
Purchase #6	$166.68	3.367%	$172.2921	$172.29	$172.30	$172.30
Purchase #7	$191.69	10.825%	$212.4404	$212.44	$212.45	$212.40
7 purchase totals =	$812.62		$870.0061	$870.01	$870.00	$870.10