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 $81.80   13.632%   $92.951   $92.95   $92.95   $93.00  
  Purchase #2 $65.47   8.784%   $71.2209   $71.22   $71.20   $71.20  
  Purchase #3 $10.51   4.396%   $10.972   $10.97   $10.95   $11.00  
  Purchase #4 $97.41   12.104%   $109.2005   $109.20   $109.20   $109.20  
  Purchase #5 $181.66   7.102%   $194.5615   $194.56   $194.55   $194.60  
  Purchase #6 $125.28   4.340%   $130.7172   $130.72   $130.70   $130.70  
  Purchase #7 $82.86   5.427%   $87.3568   $87.36   $87.35   $87.40  
  7 purchase totals = $644.99       $696.9799   $696.98   $696.90   $697.10