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	$193.49	12.575%	$217.8214	$217.82	$217.80	$217.80
Purchase #2	$212.33	3.549%	$219.8656	$219.87	$219.85	$219.90
Purchase #3	$11.65	4.618%	$12.188	$12.19	$12.20	$12.20
Purchase #4	$95.29	13.843%	$108.481	$108.48	$108.50	$108.50
Purchase #5	$53.97	10.192%	$59.4706	$59.47	$59.45	$59.50
Purchase #6	$43.71	4.275%	$45.5786	$45.58	$45.60	$45.60
Purchase #7	$128.98	7.359%	$138.4716	$138.47	$138.45	$138.50
7 purchase totals =	$739.42		$801.8768	$801.88	$801.85	$802.00