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	$95.43	9.168%	$104.179	$104.18	$104.20	$104.20
Purchase #2	$79.86	6.744%	$85.2458	$85.25	$85.25	$85.20
Purchase #3	$35.89	5.113%	$37.7251	$37.73	$37.75	$37.70
Purchase #4	$118.95	7.723%	$128.1365	$128.14	$128.15	$128.10
Purchase #5	$33.78	3.733%	$35.041	$35.04	$35.05	$35.00
Purchase #6	$13.30	13.867%	$15.1443	$15.14	$15.15	$15.10
Purchase #7	$108.34	12.748%	$122.1512	$122.15	$122.15	$122.20
7 purchase totals =	$485.55		$527.6229	$527.63	$527.70	$527.50