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	$91.26	4.530%	$95.3941	$95.39	$95.40	$95.40
Purchase #2	$34.98	13.110%	$39.5659	$39.57	$39.55	$39.60
Purchase #3	$94.34	10.141%	$103.907	$103.91	$103.90	$103.90
Purchase #4	$17.95	11.829%	$20.0733	$20.07	$20.05	$20.10
Purchase #5	$179.64	11.313%	$199.9627	$199.96	$199.95	$200.00
Purchase #6	$89.41	3.868%	$92.8684	$92.87	$92.85	$92.90
Purchase #7	$37.50	6.638%	$39.9893	$39.99	$40.00	$40.00
7 purchase totals =	$545.08		$591.7607	$591.76	$591.70	$591.90