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	$213.35	8.176%	$230.7935	$230.79	$230.80	$230.80
Purchase #2	$130.56	5.160%	$137.2969	$137.30	$137.30	$137.30
Purchase #3	$246.78	10.185%	$271.9145	$271.91	$271.90	$271.90
Purchase #4	$134.64	8.854%	$146.561	$146.56	$146.55	$146.60
Purchase #5	$154.39	11.432%	$172.0399	$172.04	$172.05	$172.00
Purchase #6	$71.88	8.675%	$78.1156	$78.12	$78.10	$78.10
Purchase #7	$102.29	10.330%	$112.8566	$112.86	$112.85	$112.90
7 purchase totals =	$1,053.89		$1,149.5780	$1,149.58	$1,149.55	$1,149.60