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	$40.96	10.856%	$45.4066	$45.41	$45.40	$45.40
Purchase #2	$187.96	8.538%	$204.008	$204.01	$204.00	$204.00
Purchase #3	$34.71	10.863%	$38.4805	$38.48	$38.50	$38.50
Purchase #4	$210.30	5.774%	$222.4427	$222.44	$222.45	$222.40
Purchase #5	$50.93	12.328%	$57.2087	$57.21	$57.20	$57.20
Purchase #6	$113.50	13.269%	$128.5603	$128.56	$128.55	$128.60
Purchase #7	$66.65	6.582%	$71.0369	$71.04	$71.05	$71.00
7 purchase totals =	$705.01		$767.1437	$767.15	$767.15	$767.10