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	$133.97	12.800%	$151.1182	$151.12	$151.10	$151.10
Purchase #2	$32.46	8.707%	$35.2863	$35.29	$35.30	$35.30
Purchase #3	$101.42	11.271%	$112.851	$112.85	$112.85	$112.90
Purchase #4	$100.40	4.863%	$105.2825	$105.28	$105.30	$105.30
Purchase #5	$119.64	6.229%	$127.0924	$127.09	$127.10	$127.10
Purchase #6	$81.43	3.750%	$84.4836	$84.48	$84.50	$84.50
Purchase #7	$114.63	13.439%	$130.0351	$130.04	$130.05	$130.00
7 purchase totals =	$683.95		$746.1491	$746.15	$746.20	$746.20