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	$191.34	13.229%	$216.6524	$216.65	$216.65	$216.70
Purchase #2	$42.36	7.395%	$45.4925	$45.49	$45.50	$45.50
Purchase #3	$116.99	11.484%	$130.4251	$130.43	$130.45	$130.40
Purchase #4	$97.59	6.491%	$103.9246	$103.92	$103.90	$103.90
Purchase #5	$182.73	6.749%	$195.0624	$195.06	$195.05	$195.10
Purchase #6	$39.68	5.282%	$41.7759	$41.78	$41.80	$41.80
Purchase #7	$65.92	9.516%	$72.1929	$72.19	$72.20	$72.20
7 purchase totals =	$736.61		$805.5258	$805.52	$805.55	$805.60