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	$192.96	6.387%	$205.2844	$205.28	$205.30	$205.30
Purchase #2	$88.82	13.387%	$100.7103	$100.71	$100.70	$100.70
Purchase #3	$110.84	12.180%	$124.3403	$124.34	$124.35	$124.30
Purchase #4	$40.51	11.736%	$45.2643	$45.26	$45.25	$45.30
Purchase #5	$183.92	5.283%	$193.6365	$193.64	$193.65	$193.60
Purchase #6	$192.89	11.586%	$215.2382	$215.24	$215.25	$215.20
Purchase #7	$53.77	10.709%	$59.5282	$59.53	$59.55	$59.50
7 purchase totals =	$863.71		$944.0022	$944.00	$944.05	$943.90