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	$85.37	7.559%	$91.8231	$91.82	$91.80	$91.80
Purchase #2	$10.25	3.642%	$10.6233	$10.62	$10.60	$10.60
Purchase #3	$107.45	9.784%	$117.9629	$117.96	$117.95	$118.00
Purchase #4	$144.40	5.449%	$152.2684	$152.27	$152.25	$152.30
Purchase #5	$247.36	3.191%	$255.2533	$255.25	$255.25	$255.30
Purchase #6	$161.77	12.764%	$182.4183	$182.42	$182.40	$182.40
Purchase #7	$11.56	5.620%	$12.2097	$12.21	$12.20	$12.20
7 purchase totals =	$768.16		$822.5590	$822.55	$822.45	$822.60