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 $39.31   4.759%   $41.1808   $41.18   $41.20   $41.20  
  Purchase #2 $232.80   5.286%   $245.1058   $245.11   $245.10   $245.10  
  Purchase #3 $43.57   4.249%   $45.4213   $45.42   $45.40   $45.40  
  Purchase #4 $220.26   5.523%   $232.425   $232.43   $232.45   $232.40  
  Purchase #5 $24.79   12.525%   $27.8949   $27.89   $27.90   $27.90  
  Purchase #6 $94.93   9.785%   $104.2189   $104.22   $104.20   $104.20  
  Purchase #7 $58.49   12.515%   $65.81   $65.81   $65.80   $65.80  
  7 purchase totals = $714.15       $762.0567   $762.06   $762.05   $762.00