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	$120.44	4.676%	$126.0718	$126.07	$126.05	$126.10
Purchase #2	$12.40	8.650%	$13.4726	$13.47	$13.45	$13.50
Purchase #3	$166.84	12.568%	$187.8085	$187.81	$187.80	$187.80
Purchase #4	$145.38	10.598%	$160.7874	$160.79	$160.80	$160.80
Purchase #5	$176.30	12.503%	$198.3428	$198.34	$198.35	$198.30
Purchase #6	$72.43	13.213%	$82.0002	$82.00	$82.00	$82.00
Purchase #7	$34.78	7.466%	$37.3767	$37.38	$37.40	$37.40
7 purchase totals =	$728.57		$805.8600	$805.86	$805.85	$805.90