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	$86.93	5.631%	$91.825	$91.83	$91.85	$91.80
Purchase #2	$205.88	8.263%	$222.8919	$222.89	$222.90	$222.90
Purchase #3	$157.43	5.394%	$165.9218	$165.92	$165.90	$165.90
Purchase #4	$12.49	10.785%	$13.837	$13.84	$13.85	$13.80
Purchase #5	$155.43	5.479%	$163.946	$163.95	$163.95	$163.90
Purchase #6	$243.76	12.704%	$274.7273	$274.73	$274.75	$274.70
Purchase #7	$207.63	7.145%	$222.4652	$222.47	$222.45	$222.50
7 purchase totals =	$1,069.55		$1,155.6142	$1,155.63	$1,155.65	$1,155.50