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	$157.34	7.234%	$168.722	$168.72	$168.70	$168.70
Purchase #2	$103.82	11.805%	$116.076	$116.08	$116.10	$116.10
Purchase #3	$53.77	10.300%	$59.3083	$59.31	$59.30	$59.30
Purchase #4	$213.81	4.782%	$224.0344	$224.03	$224.05	$224.00
Purchase #5	$154.30	9.649%	$169.1884	$169.19	$169.20	$169.20
Purchase #6	$29.32	3.325%	$30.2949	$30.29	$30.30	$30.30
Purchase #7	$217.72	8.791%	$236.8598	$236.86	$236.85	$236.90
7 purchase totals =	$930.08		$1,004.4838	$1,004.48	$1,004.50	$1,004.50