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	$214.92	12.844%	$242.5243	$242.52	$242.50	$242.50
Purchase #2	$139.44	4.332%	$145.4805	$145.48	$145.50	$145.50
Purchase #3	$114.85	13.548%	$130.4099	$130.41	$130.40	$130.40
Purchase #4	$212.30	4.569%	$222	$222.00	$222.00	$222.00
Purchase #5	$139.28	13.107%	$157.5354	$157.54	$157.55	$157.50
Purchase #6	$84.74	4.309%	$88.3914	$88.39	$88.40	$88.40
Purchase #7	$46.85	3.434%	$48.4588	$48.46	$48.45	$48.50
7 purchase totals =	$952.38		$1,034.8003	$1,034.80	$1,034.80	$1,034.80