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	$119.54	9.515%	$130.9142	$130.91	$130.90	$130.90
Purchase #2	$208.42	3.360%	$215.4229	$215.42	$215.40	$215.40
Purchase #3	$13.51	11.402%	$15.0504	$15.05	$15.05	$15.10
Purchase #4	$32.32	10.330%	$35.6587	$35.66	$35.65	$35.70
Purchase #5	$235.45	11.267%	$261.9782	$261.98	$262.00	$262.00
Purchase #6	$150.31	11.633%	$167.7956	$167.80	$167.80	$167.80
Purchase #7	$92.92	8.226%	$100.5636	$100.56	$100.55	$100.60
7 purchase totals =	$852.47		$927.3836	$927.38	$927.35	$927.50