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	$37.79	8.241%	$40.9043	$40.90	$40.90	$40.90
Purchase #2	$14.45	11.186%	$16.0664	$16.07	$16.05	$16.10
Purchase #3	$10.25	11.600%	$11.439	$11.44	$11.45	$11.40
Purchase #4	$17.49	4.166%	$18.2186	$18.22	$18.20	$18.20
Purchase #5	$78.72	11.629%	$87.8743	$87.87	$87.85	$87.90
Purchase #6	$204.30	6.352%	$217.2771	$217.28	$217.30	$217.30
Purchase #7	$46.88	11.118%	$52.0921	$52.09	$52.10	$52.10
7 purchase totals =	$409.88		$443.8718	$443.87	$443.85	$443.90