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 $23.59   8.507%   $25.5968   $25.60   $25.60   $25.60  
  Purchase #2 $233.35   5.282%   $245.6755   $245.68   $245.70   $245.70  
  Purchase #3 $183.84   8.133%   $198.7917   $198.79   $198.80   $198.80  
  Purchase #4 $10.75   12.469%   $12.0904   $12.09   $12.10   $12.10  
  Purchase #5 $236.54   6.137%   $251.0565   $251.06   $251.05   $251.10  
  Purchase #6 $161.51   5.746%   $170.7904   $170.79   $170.80   $170.80  
  Purchase #7 $229.46   4.122%   $238.9183   $238.92   $238.90   $238.90  
  7 purchase totals = $1,079.04       $1,142.9196   $1,142.93   $1,142.95   $1,143.00