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	$32.90	6.451%	$35.0224	$35.02	$35.00	$35.00
Purchase #2	$43.39	13.716%	$49.3414	$49.34	$49.35	$49.30
Purchase #3	$211.65	8.389%	$229.4053	$229.41	$229.40	$229.40
Purchase #4	$41.47	4.861%	$43.4859	$43.49	$43.50	$43.50
Purchase #5	$154.78	11.476%	$172.5426	$172.54	$172.55	$172.50
Purchase #6	$118.29	11.516%	$131.9123	$131.91	$131.90	$131.90
Purchase #7	$227.36	6.679%	$242.5454	$242.55	$242.55	$242.50
7 purchase totals =	$829.84		$904.2553	$904.26	$904.25	$904.10