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 $150.58   9.567%   $164.986   $164.99   $165.00   $165.00  
  Purchase #2 $229.56   3.191%   $236.8853   $236.89   $236.90   $236.90  
  Purchase #3 $85.69   11.265%   $95.343   $95.34   $95.35   $95.30  
  Purchase #4 $227.50   13.824%   $258.9496   $258.95   $258.95   $258.90  
  Purchase #5 $61.37   6.273%   $65.2197   $65.22   $65.20   $65.20  
  Purchase #6 $57.51   12.445%   $64.6671   $64.67   $64.65   $64.70  
  Purchase #7 $160.36   8.637%   $174.2103   $174.21   $174.20   $174.20  
  7 purchase totals = $972.57       $1,060.2610   $1,060.27   $1,060.25   $1,060.20