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	$130.82	12.185%	$146.7604	$146.76	$146.75	$146.80
Purchase #2	$101.71	3.583%	$105.3543	$105.35	$105.35	$105.40
Purchase #3	$159.89	11.633%	$178.49	$178.49	$178.50	$178.50
Purchase #4	$195.35	8.774%	$212.49	$212.49	$212.50	$212.50
Purchase #5	$188.83	7.620%	$203.2188	$203.22	$203.20	$203.20
Purchase #6	$43.30	5.194%	$45.549	$45.55	$45.55	$45.50
Purchase #7	$135.82	9.414%	$148.6061	$148.61	$148.60	$148.60
7 purchase totals =	$955.72		$1,040.4686	$1,040.47	$1,040.45	$1,040.50