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	$125.47	7.506%	$134.8878	$134.89	$134.90	$134.90
Purchase #2	$73.30	4.861%	$76.8631	$76.86	$76.85	$76.90
Purchase #3	$172.70	13.670%	$196.3081	$196.31	$196.30	$196.30
Purchase #4	$182.64	4.539%	$190.93	$190.93	$190.95	$190.90
Purchase #5	$157.32	9.297%	$171.946	$171.95	$171.95	$171.90
Purchase #6	$30.83	6.325%	$32.78	$32.78	$32.80	$32.80
Purchase #7	$222.56	9.531%	$243.7722	$243.77	$243.75	$243.80
7 purchase totals =	$964.82		$1,047.4872	$1,047.49	$1,047.50	$1,047.50