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	$143.48	5.670%	$151.6153	$151.62	$151.60	$151.60
Purchase #2	$35.67	5.476%	$37.6233	$37.62	$37.60	$37.60
Purchase #3	$9.42	11.236%	$10.4784	$10.48	$10.50	$10.50
Purchase #4	$53.61	3.429%	$55.4483	$55.45	$55.45	$55.40
Purchase #5	$110.84	10.310%	$122.2676	$122.27	$122.25	$122.30
Purchase #6	$84.43	7.626%	$90.8686	$90.87	$90.85	$90.90
Purchase #7	$127.79	12.147%	$143.3127	$143.31	$143.30	$143.30
7 purchase totals =	$565.24		$611.6142	$611.62	$611.55	$611.60