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	$229.25	3.569%	$237.4319	$237.43	$237.45	$237.40
Purchase #2	$192.76	11.462%	$214.8542	$214.85	$214.85	$214.90
Purchase #3	$130.83	8.649%	$142.1455	$142.15	$142.15	$142.10
Purchase #4	$35.87	9.532%	$39.2891	$39.29	$39.30	$39.30
Purchase #5	$249.85	9.845%	$274.4477	$274.45	$274.45	$274.40
Purchase #6	$94.77	4.772%	$99.2924	$99.29	$99.30	$99.30
Purchase #7	$242.32	6.827%	$258.8632	$258.86	$258.85	$258.90
7 purchase totals =	$1,175.65		$1,266.3240	$1,266.32	$1,266.35	$1,266.30