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	$89.79	6.313%	$95.4584	$95.46	$95.45	$95.50
Purchase #2	$5.53	5.105%	$5.8123	$5.81	$5.80	$5.80
Purchase #3	$242.42	11.471%	$270.228	$270.23	$270.25	$270.20
Purchase #4	$180.68	5.341%	$190.3301	$190.33	$190.35	$190.30
Purchase #5	$125.37	13.494%	$142.2874	$142.29	$142.30	$142.30
Purchase #6	$175.83	5.448%	$185.4092	$185.41	$185.40	$185.40
Purchase #7	$44.32	11.475%	$49.4057	$49.41	$49.40	$49.40
7 purchase totals =	$863.94		$938.9311	$938.94	$938.95	$938.90