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	$76.51	7.707%	$82.4066	$82.41	$82.40	$82.40
Purchase #2	$135.58	7.851%	$146.2244	$146.22	$146.20	$146.20
Purchase #3	$145.42	13.312%	$164.7783	$164.78	$164.80	$164.80
Purchase #4	$217.43	10.665%	$240.6189	$240.62	$240.60	$240.60
Purchase #5	$36.41	11.492%	$40.5942	$40.59	$40.60	$40.60
Purchase #6	$164.89	12.611%	$185.6843	$185.68	$185.70	$185.70
Purchase #7	$185.50	3.855%	$192.651	$192.65	$192.65	$192.70
7 purchase totals =	$961.74		$1,052.9577	$1,052.95	$1,052.95	$1,053.00