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	$10.45	6.229%	$11.1009	$11.10	$11.10	$11.10
Purchase #2	$71.94	9.347%	$78.6642	$78.66	$78.65	$78.70
Purchase #3	$111.80	11.832%	$125.0282	$125.03	$125.05	$125.00
Purchase #4	$142.81	8.733%	$155.2816	$155.28	$155.30	$155.30
Purchase #5	$89.30	6.814%	$95.3849	$95.38	$95.40	$95.40
Purchase #6	$120.65	9.824%	$132.5027	$132.50	$132.50	$132.50
Purchase #7	$98.42	4.689%	$103.0349	$103.03	$103.05	$103.00
7 purchase totals =	$645.37		$700.9974	$700.98	$701.05	$701.00