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	$176.41	13.358%	$199.9748	$199.97	$199.95	$200.00
Purchase #2	$54.35	10.162%	$59.873	$59.87	$59.85	$59.90
Purchase #3	$227.93	12.692%	$256.8589	$256.86	$256.85	$256.90
Purchase #4	$146.99	6.431%	$156.4429	$156.44	$156.45	$156.40
Purchase #5	$12.77	8.117%	$13.8065	$13.81	$13.80	$13.80
Purchase #6	$39.76	10.375%	$43.8851	$43.89	$43.90	$43.90
Purchase #7	$24.27	7.415%	$26.0696	$26.07	$26.05	$26.10
7 purchase totals =	$682.48		$756.9108	$756.91	$756.85	$757.00