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	$117.64	7.616%	$126.5995	$126.60	$126.60	$126.60
Purchase #2	$158.84	8.752%	$172.7417	$172.74	$172.75	$172.70
Purchase #3	$47.31	12.129%	$53.0482	$53.05	$53.05	$53.00
Purchase #4	$83.39	8.177%	$90.2088	$90.21	$90.20	$90.20
Purchase #5	$79.69	6.719%	$85.0444	$85.04	$85.05	$85.00
Purchase #6	$227.40	6.188%	$241.4715	$241.47	$241.45	$241.50
Purchase #7	$53.39	7.453%	$57.3692	$57.37	$57.35	$57.40
7 purchase totals =	$767.66		$826.4833	$826.48	$826.45	$826.40