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	$218.55	11.703%	$244.1269	$244.13	$244.15	$244.10
Purchase #2	$153.64	9.390%	$168.0668	$168.07	$168.05	$168.10
Purchase #3	$38.39	5.762%	$40.602	$40.60	$40.60	$40.60
Purchase #4	$174.62	6.412%	$185.8166	$185.82	$185.80	$185.80
Purchase #5	$141.89	9.457%	$155.3085	$155.31	$155.30	$155.30
Purchase #6	$118.67	6.456%	$126.3313	$126.33	$126.35	$126.30
Purchase #7	$37.83	7.128%	$40.5265	$40.53	$40.55	$40.50
7 purchase totals =	$883.59		$960.7786	$960.79	$960.80	$960.70