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	$247.59	7.700%	$266.6544	$266.65	$266.65	$266.70
Purchase #2	$33.69	11.452%	$37.5482	$37.55	$37.55	$37.50
Purchase #3	$6.34	11.349%	$7.0595	$7.06	$7.05	$7.10
Purchase #4	$16.68	11.171%	$18.5433	$18.54	$18.55	$18.50
Purchase #5	$78.50	12.123%	$88.0166	$88.02	$88.00	$88.00
Purchase #6	$124.93	12.470%	$140.5088	$140.51	$140.50	$140.50
Purchase #7	$234.99	9.154%	$256.501	$256.50	$256.50	$256.50
7 purchase totals =	$742.72		$814.8318	$814.83	$814.80	$814.80