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	$195.59	11.223%	$217.5411	$217.54	$217.55	$217.50
Purchase #2	$83.89	6.163%	$89.0601	$89.06	$89.05	$89.10
Purchase #3	$190.92	12.381%	$214.5578	$214.56	$214.55	$214.60
Purchase #4	$11.53	13.860%	$13.1281	$13.13	$13.15	$13.10
Purchase #5	$71.41	7.131%	$76.5022	$76.50	$76.50	$76.50
Purchase #6	$40.67	9.598%	$44.5735	$44.57	$44.55	$44.60
Purchase #7	$249.56	6.512%	$265.8113	$265.81	$265.80	$265.80
7 purchase totals =	$843.57		$921.1741	$921.17	$921.15	$921.20