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	$56.49	4.719%	$59.1558	$59.16	$59.15	$59.20
Purchase #2	$67.26	7.457%	$72.2756	$72.28	$72.30	$72.30
Purchase #3	$105.95	12.722%	$119.429	$119.43	$119.45	$119.40
Purchase #4	$214.43	10.353%	$236.6299	$236.63	$236.65	$236.60
Purchase #5	$158.43	8.297%	$171.5749	$171.57	$171.55	$171.60
Purchase #6	$18.50	9.102%	$20.1839	$20.18	$20.20	$20.20
Purchase #7	$227.78	12.202%	$255.5737	$255.57	$255.55	$255.60
7 purchase totals =	$848.84		$934.8228	$934.82	$934.85	$934.90