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	$85.51	9.660%	$93.7703	$93.77	$93.75	$93.80
Purchase #2	$78.50	9.442%	$85.912	$85.91	$85.90	$85.90
Purchase #3	$231.59	5.861%	$245.1635	$245.16	$245.15	$245.20
Purchase #4	$38.93	12.341%	$43.7344	$43.73	$43.75	$43.70
Purchase #5	$147.79	11.668%	$165.0341	$165.03	$165.05	$165.00
Purchase #6	$35.56	11.398%	$39.6131	$39.61	$39.60	$39.60
Purchase #7	$149.45	12.268%	$167.7845	$167.78	$167.80	$167.80
7 purchase totals =	$767.33		$841.0119	$840.99	$841.00	$841.00