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	$232.33	4.847%	$243.591	$243.59	$243.60	$243.60
Purchase #2	$32.70	7.853%	$35.2679	$35.27	$35.25	$35.30
Purchase #3	$226.35	5.166%	$238.0432	$238.04	$238.05	$238.00
Purchase #4	$140.93	12.505%	$158.5533	$158.55	$158.55	$158.60
Purchase #5	$165.71	7.757%	$178.5641	$178.56	$178.55	$178.60
Purchase #6	$205.25	6.291%	$218.1623	$218.16	$218.15	$218.20
Purchase #7	$52.44	13.422%	$59.4785	$59.48	$59.50	$59.50
7 purchase totals =	$1,055.71		$1,131.6603	$1,131.65	$1,131.65	$1,131.80