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	$100.42	11.779%	$112.2485	$112.25	$112.25	$112.20
Purchase #2	$167.78	7.589%	$180.5128	$180.51	$180.50	$180.50
Purchase #3	$230.91	8.472%	$250.4727	$250.47	$250.45	$250.50
Purchase #4	$135.53	10.121%	$149.247	$149.25	$149.25	$149.20
Purchase #5	$15.39	13.375%	$17.4484	$17.45	$17.45	$17.40
Purchase #6	$98.83	3.809%	$102.5944	$102.59	$102.60	$102.60
Purchase #7	$196.92	11.205%	$218.9849	$218.98	$219.00	$219.00
7 purchase totals =	$945.78		$1,031.5087	$1,031.50	$1,031.50	$1,031.40