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 $123.55   7.603%   $132.9435   $132.94   $132.95   $132.90  
  Purchase #2 $58.52   8.683%   $63.6013   $63.60   $63.60   $63.60  
  Purchase #3 $67.60   7.641%   $72.7653   $72.77   $72.75   $72.80  
  Purchase #4 $89.83   7.178%   $96.278   $96.28   $96.30   $96.30  
  Purchase #5 $148.80   6.250%   $158.1   $158.10   $158.10   $158.10  
  Purchase #6 $146.75   11.377%   $163.4457   $163.45   $163.45   $163.40  
  Purchase #7 $61.59   10.357%   $67.9689   $67.97   $67.95   $68.00  
  7 purchase totals = $696.64       $755.1027   $755.11   $755.10   $755.10