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	$94.54	11.869%	$105.761	$105.76	$105.75	$105.80
Purchase #2	$224.25	11.403%	$249.8212	$249.82	$249.80	$249.80
Purchase #3	$149.78	11.105%	$166.4131	$166.41	$166.40	$166.40
Purchase #4	$147.84	8.650%	$160.6282	$160.63	$160.65	$160.60
Purchase #5	$189.69	13.565%	$215.4214	$215.42	$215.40	$215.40
Purchase #6	$32.62	9.744%	$35.7985	$35.80	$35.80	$35.80
Purchase #7	$146.96	3.400%	$151.9566	$151.96	$151.95	$152.00
7 purchase totals =	$985.68		$1,085.8000	$1,085.80	$1,085.75	$1,085.80