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	$32.36	10.769%	$35.8448	$35.84	$35.85	$35.80
Purchase #2	$137.64	13.493%	$156.2118	$156.21	$156.20	$156.20
Purchase #3	$21.50	5.687%	$22.7227	$22.72	$22.70	$22.70
Purchase #4	$146.50	12.537%	$164.8667	$164.87	$164.85	$164.90
Purchase #5	$185.87	12.319%	$208.7673	$208.77	$208.75	$208.80
Purchase #6	$55.89	6.390%	$59.4614	$59.46	$59.45	$59.50
Purchase #7	$154.98	13.464%	$175.8465	$175.85	$175.85	$175.80
7 purchase totals =	$734.74		$823.7212	$823.72	$823.65	$823.70