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	$147.31	13.650%	$167.4178	$167.42	$167.40	$167.40
Purchase #2	$165.55	4.220%	$172.5362	$172.54	$172.55	$172.50
Purchase #3	$12.59	7.286%	$13.5073	$13.51	$13.50	$13.50
Purchase #4	$33.50	4.698%	$35.0738	$35.07	$35.05	$35.10
Purchase #5	$246.31	11.474%	$274.5716	$274.57	$274.55	$274.60
Purchase #6	$34.30	9.726%	$37.636	$37.64	$37.65	$37.60
Purchase #7	$26.30	13.777%	$29.9234	$29.92	$29.90	$29.90
7 purchase totals =	$665.86		$730.6661	$730.67	$730.60	$730.60