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	$82.40	9.353%	$90.1069	$90.11	$90.10	$90.10
Purchase #2	$190.32	8.123%	$205.7797	$205.78	$205.80	$205.80
Purchase #3	$81.72	11.508%	$91.1243	$91.12	$91.10	$91.10
Purchase #4	$52.76	4.313%	$55.0355	$55.04	$55.05	$55.00
Purchase #5	$190.85	4.434%	$199.3123	$199.31	$199.30	$199.30
Purchase #6	$181.76	4.867%	$190.6063	$190.61	$190.60	$190.60
Purchase #7	$144.94	13.126%	$163.9648	$163.96	$163.95	$164.00
7 purchase totals =	$924.75		$995.9298	$995.93	$995.90	$995.90