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	$89.47	6.248%	$95.0601	$95.06	$95.05	$95.10
Purchase #2	$93.66	11.694%	$104.6126	$104.61	$104.60	$104.60
Purchase #3	$198.81	8.820%	$216.345	$216.35	$216.35	$216.30
Purchase #4	$99.67	11.350%	$110.9825	$110.98	$111.00	$111.00
Purchase #5	$40.75	11.718%	$45.5251	$45.53	$45.55	$45.50
Purchase #6	$189.27	13.273%	$214.3918	$214.39	$214.40	$214.40
Purchase #7	$65.82	7.245%	$70.5887	$70.59	$70.60	$70.60
7 purchase totals =	$777.45		$857.5058	$857.51	$857.55	$857.50