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	$141.87	4.221%	$147.8583	$147.86	$147.85	$147.90
Purchase #2	$61.81	8.443%	$67.0286	$67.03	$67.05	$67.00
Purchase #3	$196.58	13.443%	$223.0062	$223.01	$223.00	$223.00
Purchase #4	$201.66	12.794%	$227.4604	$227.46	$227.45	$227.50
Purchase #5	$83.53	4.697%	$87.4534	$87.45	$87.45	$87.50
Purchase #6	$69.93	12.420%	$78.6153	$78.62	$78.60	$78.60
Purchase #7	$197.89	6.475%	$210.7034	$210.70	$210.70	$210.70
7 purchase totals =	$953.27		$1,042.1256	$1,042.13	$1,042.10	$1,042.20