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	$153.25	5.716%	$162.0098	$162.01	$162.00	$162.00
Purchase #2	$40.37	11.624%	$45.0626	$45.06	$45.05	$45.10
Purchase #3	$227.33	8.717%	$247.1464	$247.15	$247.15	$247.10
Purchase #4	$12.49	6.110%	$13.2531	$13.25	$13.25	$13.30
Purchase #5	$157.55	13.760%	$179.2289	$179.23	$179.25	$179.20
Purchase #6	$154.84	4.856%	$162.359	$162.36	$162.35	$162.40
Purchase #7	$141.33	3.653%	$146.4928	$146.49	$146.50	$146.50
7 purchase totals =	$887.16		$955.5526	$955.55	$955.55	$955.60