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	$38.50	7.691%	$41.461	$41.46	$41.45	$41.50
Purchase #2	$12.54	7.348%	$13.4614	$13.46	$13.45	$13.50
Purchase #3	$158.31	13.551%	$179.7626	$179.76	$179.75	$179.80
Purchase #4	$196.56	13.267%	$222.6376	$222.64	$222.65	$222.60
Purchase #5	$65.26	9.842%	$71.6829	$71.68	$71.70	$71.70
Purchase #6	$206.72	9.603%	$226.5713	$226.57	$226.55	$226.60
Purchase #7	$44.42	8.630%	$48.2534	$48.25	$48.25	$48.30
7 purchase totals =	$722.31		$803.8302	$803.82	$803.80	$804.00