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	$167.51	10.513%	$185.1203	$185.12	$185.10	$185.10
Purchase #2	$63.55	13.721%	$72.2697	$72.27	$72.25	$72.30
Purchase #3	$113.50	8.733%	$123.412	$123.41	$123.40	$123.40
Purchase #4	$77.32	8.306%	$83.7422	$83.74	$83.75	$83.70
Purchase #5	$95.79	10.781%	$106.1171	$106.12	$106.10	$106.10
Purchase #6	$214.42	11.383%	$238.8274	$238.83	$238.85	$238.80
Purchase #7	$143.62	4.309%	$149.8086	$149.81	$149.80	$149.80
7 purchase totals =	$875.71		$959.2973	$959.30	$959.25	$959.20