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	$200.26	7.733%	$215.7461	$215.75	$215.75	$215.70
Purchase #2	$66.91	7.689%	$72.0547	$72.05	$72.05	$72.10
Purchase #3	$140.69	4.193%	$146.5891	$146.59	$146.60	$146.60
Purchase #4	$232.73	11.831%	$260.2643	$260.26	$260.25	$260.30
Purchase #5	$29.29	13.434%	$33.2248	$33.22	$33.20	$33.20
Purchase #6	$33.40	13.402%	$37.8763	$37.88	$37.90	$37.90
Purchase #7	$156.93	11.547%	$175.0507	$175.05	$175.05	$175.10
7 purchase totals =	$860.21		$940.8060	$940.80	$940.80	$940.90