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	$152.62	6.472%	$162.4976	$162.50	$162.50	$162.50
Purchase #2	$137.42	7.763%	$148.0879	$148.09	$148.10	$148.10
Purchase #3	$130.33	13.791%	$148.3038	$148.30	$148.30	$148.30
Purchase #4	$191.37	8.137%	$206.9418	$206.94	$206.95	$206.90
Purchase #5	$13.43	6.728%	$14.3336	$14.33	$14.35	$14.30
Purchase #6	$57.83	5.452%	$60.9829	$60.98	$61.00	$61.00
Purchase #7	$73.53	7.114%	$78.7609	$78.76	$78.75	$78.80
7 purchase totals =	$756.53		$819.9085	$819.90	$819.95	$819.90