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 $86.80   9.840%   $95.3411   $95.34   $95.35   $95.30  
  Purchase #2 $208.59   4.422%   $217.8138   $217.81   $217.80   $217.80  
  Purchase #3 $247.72   6.783%   $264.5228   $264.52   $264.50   $264.50  
  Purchase #4 $131.70   12.520%   $148.1888   $148.19   $148.20   $148.20  
  Purchase #5 $101.36   5.235%   $106.6662   $106.67   $106.65   $106.70  
  Purchase #6 $169.73   5.791%   $179.5591   $179.56   $179.55   $179.60  
  Purchase #7 $86.97   3.795%   $90.2705   $90.27   $90.25   $90.30  
  7 purchase totals = $1,032.87       $1,102.3623   $1,102.36   $1,102.30   $1,102.40