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	$197.35	8.188%	$213.509	$213.51	$213.50	$213.50
Purchase #2	$155.42	6.354%	$165.2954	$165.30	$165.30	$165.30
Purchase #3	$97.62	3.293%	$100.8346	$100.83	$100.85	$100.80
Purchase #4	$37.76	12.568%	$42.5057	$42.51	$42.50	$42.50
Purchase #5	$138.64	12.452%	$155.9035	$155.90	$155.90	$155.90
Purchase #6	$32.64	9.133%	$35.621	$35.62	$35.60	$35.60
Purchase #7	$203.33	6.833%	$217.2235	$217.22	$217.20	$217.20
7 purchase totals =	$862.76		$930.8927	$930.89	$930.85	$930.80