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	$184.29	3.556%	$190.8434	$190.84	$190.85	$190.80
Purchase #2	$192.67	4.255%	$200.8681	$200.87	$200.85	$200.90
Purchase #3	$169.28	4.768%	$177.3513	$177.35	$177.35	$177.40
Purchase #4	$189.32	13.375%	$214.6416	$214.64	$214.65	$214.60
Purchase #5	$131.37	5.820%	$139.0157	$139.02	$139.00	$139.00
Purchase #6	$37.64	13.194%	$42.6062	$42.61	$42.60	$42.60
Purchase #7	$181.49	9.806%	$199.2869	$199.29	$199.30	$199.30
7 purchase totals =	$1,086.06		$1,164.6132	$1,164.62	$1,164.60	$1,164.60