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	$202.50	3.162%	$208.9031	$208.90	$208.90	$208.90
Purchase #2	$64.52	13.357%	$73.1379	$73.14	$73.15	$73.10
Purchase #3	$32.34	7.767%	$34.8518	$34.85	$34.85	$34.90
Purchase #4	$221.70	7.370%	$238.0393	$238.04	$238.05	$238.00
Purchase #5	$89.33	12.821%	$100.783	$100.78	$100.80	$100.80
Purchase #6	$93.95	6.694%	$100.239	$100.24	$100.25	$100.20
Purchase #7	$8.97	13.791%	$10.2071	$10.21	$10.20	$10.20
7 purchase totals =	$713.31		$766.1612	$766.16	$766.20	$766.10