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	$157.83	11.314%	$175.6869	$175.69	$175.70	$175.70
Purchase #2	$20.33	5.447%	$21.4374	$21.44	$21.45	$21.40
Purchase #3	$190.52	11.259%	$211.9706	$211.97	$211.95	$212.00
Purchase #4	$21.99	11.400%	$24.4969	$24.50	$24.50	$24.50
Purchase #5	$155.77	6.259%	$165.5196	$165.52	$165.50	$165.50
Purchase #6	$196.46	4.762%	$205.8154	$205.82	$205.80	$205.80
Purchase #7	$7.46	5.738%	$7.8881	$7.89	$7.90	$7.90
7 purchase totals =	$750.36		$812.8149	$812.83	$812.80	$812.80