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	$79.51	3.276%	$82.1147	$82.11	$82.10	$82.10
Purchase #2	$42.95	13.434%	$48.7199	$48.72	$48.70	$48.70
Purchase #3	$41.52	10.573%	$45.9099	$45.91	$45.90	$45.90
Purchase #4	$57.30	10.744%	$63.4563	$63.46	$63.45	$63.50
Purchase #5	$40.87	6.707%	$43.6112	$43.61	$43.60	$43.60
Purchase #6	$20.83	11.398%	$23.2042	$23.20	$23.20	$23.20
Purchase #7	$216.32	4.231%	$225.4725	$225.47	$225.45	$225.50
7 purchase totals =	$499.30		$532.4887	$532.48	$532.40	$532.50