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	$164.63	12.437%	$185.105	$185.11	$185.10	$185.10
Purchase #2	$35.58	5.847%	$37.6604	$37.66	$37.65	$37.70
Purchase #3	$185.47	8.791%	$201.7747	$201.77	$201.75	$201.80
Purchase #4	$248.58	12.264%	$279.0659	$279.07	$279.05	$279.10
Purchase #5	$81.94	11.789%	$91.5999	$91.60	$91.60	$91.60
Purchase #6	$84.96	12.308%	$95.4169	$95.42	$95.40	$95.40
Purchase #7	$168.25	13.375%	$190.7534	$190.75	$190.75	$190.80
7 purchase totals =	$969.41		$1,081.3762	$1,081.38	$1,081.30	$1,081.50