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 $10.87   6.632%   $11.5909   $11.59   $11.60   $11.60  
  Purchase #2 $212.70   10.825%   $235.7248   $235.72   $235.70   $235.70  
  Purchase #3 $247.97   6.644%   $264.4451   $264.45   $264.45   $264.40  
  Purchase #4 $130.68   3.803%   $135.6498   $135.65   $135.65   $135.60  
  Purchase #5 $151.49   6.350%   $161.1096   $161.11   $161.10   $161.10  
  Purchase #6 $182.84   5.700%   $193.2619   $193.26   $193.25   $193.30  
  Purchase #7 $190.30   5.129%   $200.0605   $200.06   $200.05   $200.10  
  7 purchase totals = $1,126.85       $1,201.8426   $1,201.84   $1,201.80   $1,201.80