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	$193.35	13.472%	$219.3981	$219.40	$219.40	$219.40
Purchase #2	$44.37	8.216%	$48.0154	$48.02	$48.00	$48.00
Purchase #3	$80.52	3.301%	$83.178	$83.18	$83.20	$83.20
Purchase #4	$131.41	4.599%	$137.4535	$137.45	$137.45	$137.50
Purchase #5	$71.52	9.746%	$78.4903	$78.49	$78.50	$78.50
Purchase #6	$167.42	13.516%	$190.0485	$190.05	$190.05	$190.00
Purchase #7	$169.74	12.229%	$190.4975	$190.50	$190.50	$190.50
7 purchase totals =	$858.33		$947.0813	$947.09	$947.10	$947.10