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	$243.51	5.196%	$256.1628	$256.16	$256.15	$256.20
Purchase #2	$9.81	9.213%	$10.7138	$10.71	$10.70	$10.70
Purchase #3	$203.69	12.643%	$229.4425	$229.44	$229.45	$229.40
Purchase #4	$22.80	7.869%	$24.5941	$24.59	$24.60	$24.60
Purchase #5	$143.42	10.470%	$158.4361	$158.44	$158.45	$158.40
Purchase #6	$91.71	8.841%	$99.8181	$99.82	$99.80	$99.80
Purchase #7	$162.51	10.157%	$179.0161	$179.02	$179.00	$179.00
7 purchase totals =	$877.45		$958.1835	$958.18	$958.15	$958.10