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 $86.66   9.825%   $95.1743   $95.17   $95.15   $95.20  
  Purchase #2 $210.32   10.298%   $231.9788   $231.98   $232.00   $232.00  
  Purchase #3 $222.82   11.144%   $247.6511   $247.65   $247.65   $247.70  
  Purchase #4 $93.97   5.559%   $99.1938   $99.19   $99.20   $99.20  
  Purchase #5 $111.50   4.124%   $116.0983   $116.10   $116.10   $116.10  
  Purchase #6 $49.37   11.674%   $55.1335   $55.13   $55.15   $55.10  
  Purchase #7 $135.39   4.578%   $141.5882   $141.59   $141.60   $141.60  
  7 purchase totals = $910.03       $986.8180   $986.81   $986.85   $986.90