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	$118.98	9.577%	$130.3747	$130.37	$130.35	$130.40
Purchase #2	$45.53	6.746%	$48.6015	$48.60	$48.60	$48.60
Purchase #3	$229.38	6.106%	$243.3859	$243.39	$243.40	$243.40
Purchase #4	$16.50	4.375%	$17.2219	$17.22	$17.20	$17.20
Purchase #5	$116.85	11.609%	$130.4151	$130.42	$130.40	$130.40
Purchase #6	$131.70	8.139%	$142.4191	$142.42	$142.40	$142.40
Purchase #7	$94.43	12.172%	$105.924	$105.92	$105.90	$105.90
7 purchase totals =	$753.37		$818.3422	$818.34	$818.25	$818.30