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	$10.48	9.296%	$11.4542	$11.45	$11.45	$11.50
Purchase #2	$154.43	8.853%	$168.1017	$168.10	$168.10	$168.10
Purchase #3	$198.26	12.485%	$223.0128	$223.01	$223.00	$223.00
Purchase #4	$180.91	10.576%	$200.043	$200.04	$200.05	$200.00
Purchase #5	$64.90	8.554%	$70.4515	$70.45	$70.45	$70.50
Purchase #6	$88.70	12.760%	$100.0181	$100.02	$100.00	$100.00
Purchase #7	$149.89	8.539%	$162.6891	$162.69	$162.70	$162.70
7 purchase totals =	$847.57		$935.7704	$935.76	$935.75	$935.80