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	$233.54	3.356%	$241.3776	$241.38	$241.40	$241.40
Purchase #2	$74.73	12.487%	$84.0615	$84.06	$84.05	$84.10
Purchase #3	$78.94	13.322%	$89.4564	$89.46	$89.45	$89.50
Purchase #4	$83.77	10.806%	$92.8222	$92.82	$92.80	$92.80
Purchase #5	$190.55	9.282%	$208.2369	$208.24	$208.25	$208.20
Purchase #6	$11.54	13.652%	$13.1154	$13.12	$13.10	$13.10
Purchase #7	$199.69	8.602%	$216.8673	$216.87	$216.85	$216.90
7 purchase totals =	$872.76		$945.9373	$945.95	$945.90	$946.00