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	$33.87	7.539%	$36.4235	$36.42	$36.40	$36.40
Purchase #2	$129.81	10.343%	$143.2362	$143.24	$143.25	$143.20
Purchase #3	$205.88	8.520%	$223.421	$223.42	$223.40	$223.40
Purchase #4	$33.89	5.866%	$35.878	$35.88	$35.90	$35.90
Purchase #5	$168.60	4.295%	$175.8414	$175.84	$175.85	$175.80
Purchase #6	$127.56	13.472%	$144.7449	$144.74	$144.75	$144.70
Purchase #7	$85.52	7.602%	$92.0212	$92.02	$92.00	$92.00
7 purchase totals =	$785.13		$851.5662	$851.56	$851.55	$851.40