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	$84.54	7.721%	$91.0673	$91.07	$91.05	$91.10
Purchase #2	$151.86	7.720%	$163.5836	$163.58	$163.60	$163.60
Purchase #3	$223.51	3.723%	$231.8313	$231.83	$231.85	$231.80
Purchase #4	$34.76	3.111%	$35.8414	$35.84	$35.85	$35.80
Purchase #5	$178.60	11.130%	$198.4782	$198.48	$198.50	$198.50
Purchase #6	$196.43	13.275%	$222.5061	$222.51	$222.50	$222.50
Purchase #7	$105.86	11.800%	$118.3515	$118.35	$118.35	$118.40
7 purchase totals =	$975.56		$1,061.6594	$1,061.66	$1,061.70	$1,061.70