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	$45.80	3.555%	$47.4282	$47.43	$47.45	$47.40
Purchase #2	$71.58	4.293%	$74.6529	$74.65	$74.65	$74.70
Purchase #3	$32.57	5.714%	$34.431	$34.43	$34.45	$34.40
Purchase #4	$19.86	4.602%	$20.774	$20.77	$20.75	$20.80
Purchase #5	$40.79	5.266%	$42.938	$42.94	$42.95	$42.90
Purchase #6	$89.25	12.821%	$100.6927	$100.69	$100.70	$100.70
Purchase #7	$47.46	11.515%	$52.925	$52.93	$52.95	$52.90
7 purchase totals =	$347.31		$373.8418	$373.84	$373.90	$373.80