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	$208.39	7.158%	$223.3066	$223.31	$223.30	$223.30
Purchase #2	$38.77	3.289%	$40.0451	$40.05	$40.05	$40.00
Purchase #3	$226.33	13.143%	$256.0766	$256.08	$256.10	$256.10
Purchase #4	$166.94	13.172%	$188.9293	$188.93	$188.95	$188.90
Purchase #5	$31.26	13.657%	$35.5292	$35.53	$35.55	$35.50
Purchase #6	$133.56	9.653%	$146.4525	$146.45	$146.45	$146.50
Purchase #7	$33.27	4.579%	$34.7934	$34.79	$34.80	$34.80
7 purchase totals =	$838.52		$925.1327	$925.14	$925.20	$925.10