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	$201.85	9.244%	$220.509	$220.51	$220.50	$220.50
Purchase #2	$98.70	3.799%	$102.4496	$102.45	$102.45	$102.40
Purchase #3	$99.46	4.463%	$103.8989	$103.90	$103.90	$103.90
Purchase #4	$40.87	10.178%	$45.0297	$45.03	$45.05	$45.00
Purchase #5	$62.78	11.372%	$69.9193	$69.92	$69.90	$69.90
Purchase #6	$59.90	10.252%	$66.0409	$66.04	$66.05	$66.00
Purchase #7	$131.97	5.828%	$139.6612	$139.66	$139.65	$139.70
7 purchase totals =	$695.53		$747.5086	$747.51	$747.50	$747.40