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	$107.94	9.191%	$117.8608	$117.86	$117.85	$117.90
Purchase #2	$85.77	5.510%	$90.4959	$90.50	$90.50	$90.50
Purchase #3	$132.76	13.733%	$150.9919	$150.99	$151.00	$151.00
Purchase #4	$126.93	10.192%	$139.8667	$139.87	$139.85	$139.90
Purchase #5	$152.73	5.335%	$160.8781	$160.88	$160.90	$160.90
Purchase #6	$78.95	4.566%	$82.5549	$82.55	$82.55	$82.60
Purchase #7	$234.45	12.836%	$264.544	$264.54	$264.55	$264.50
7 purchase totals =	$919.53		$1,007.1923	$1,007.19	$1,007.20	$1,007.30