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	$79.66	7.672%	$85.7715	$85.77	$85.75	$85.80
Purchase #2	$59.43	11.693%	$66.3791	$66.38	$66.40	$66.40
Purchase #3	$168.76	6.469%	$179.6771	$179.68	$179.70	$179.70
Purchase #4	$8.75	6.861%	$9.3503	$9.35	$9.35	$9.40
Purchase #5	$44.59	3.477%	$46.1404	$46.14	$46.15	$46.10
Purchase #6	$54.38	13.111%	$61.5098	$61.51	$61.50	$61.50
Purchase #7	$130.84	13.295%	$148.2352	$148.24	$148.25	$148.20
7 purchase totals =	$546.41		$597.0634	$597.07	$597.10	$597.10