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	$56.84	13.312%	$64.4065	$64.41	$64.40	$64.40
Purchase #2	$234.87	4.326%	$245.0305	$245.03	$245.05	$245.00
Purchase #3	$211.49	10.390%	$233.4638	$233.46	$233.45	$233.50
Purchase #4	$60.48	11.153%	$67.2253	$67.23	$67.25	$67.20
Purchase #5	$60.89	5.856%	$64.4557	$64.46	$64.45	$64.50
Purchase #6	$32.82	13.525%	$37.2589	$37.26	$37.25	$37.30
Purchase #7	$9.79	5.268%	$10.3057	$10.31	$10.30	$10.30
7 purchase totals =	$667.18		$722.1464	$722.16	$722.15	$722.20