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	$39.36	9.577%	$43.1295	$43.13	$43.15	$43.10
Purchase #2	$87.43	13.512%	$99.2435	$99.24	$99.25	$99.20
Purchase #3	$131.64	6.706%	$140.4678	$140.47	$140.45	$140.50
Purchase #4	$67.68	7.210%	$72.5597	$72.56	$72.55	$72.60
Purchase #5	$138.51	5.654%	$146.3414	$146.34	$146.35	$146.30
Purchase #6	$100.33	13.717%	$114.0923	$114.09	$114.10	$114.10
Purchase #7	$98.49	12.387%	$110.69	$110.69	$110.70	$110.70
7 purchase totals =	$663.44		$726.5242	$726.52	$726.55	$726.50