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	$42.45	4.187%	$44.2274	$44.23	$44.25	$44.20
Purchase #2	$142.86	13.228%	$161.7575	$161.76	$161.75	$161.80
Purchase #3	$108.57	4.816%	$113.7987	$113.80	$113.80	$113.80
Purchase #4	$100.78	10.862%	$111.7267	$111.73	$111.75	$111.70
Purchase #5	$11.64	7.279%	$12.4873	$12.49	$12.50	$12.50
Purchase #6	$246.74	13.496%	$280.04	$280.04	$280.05	$280.00
Purchase #7	$51.38	12.590%	$57.8487	$57.85	$57.85	$57.80
7 purchase totals =	$704.42		$781.8863	$781.90	$781.95	$781.80