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	$35.96	4.625%	$37.6232	$37.62	$37.60	$37.60
Purchase #2	$32.56	3.697%	$33.7637	$33.76	$33.75	$33.80
Purchase #3	$158.26	6.771%	$168.9758	$168.98	$169.00	$169.00
Purchase #4	$92.69	11.477%	$103.328	$103.33	$103.35	$103.30
Purchase #5	$125.36	6.227%	$133.1662	$133.17	$133.15	$133.20
Purchase #6	$172.51	9.443%	$188.8001	$188.80	$188.80	$188.80
Purchase #7	$140.28	4.609%	$146.7455	$146.75	$146.75	$146.70
7 purchase totals =	$757.62		$812.4025	$812.41	$812.40	$812.40