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	$91.33	11.640%	$101.9608	$101.96	$101.95	$102.00
Purchase #2	$152.99	10.325%	$168.7862	$168.79	$168.80	$168.80
Purchase #3	$44.86	4.148%	$46.7208	$46.72	$46.70	$46.70
Purchase #4	$19.72	8.789%	$21.4532	$21.45	$21.45	$21.50
Purchase #5	$19.26	4.468%	$20.1205	$20.12	$20.10	$20.10
Purchase #6	$45.94	13.213%	$52.0101	$52.01	$52.00	$52.00
Purchase #7	$61.29	12.431%	$68.909	$68.91	$68.90	$68.90
7 purchase totals =	$435.39		$479.9606	$479.96	$479.90	$480.00