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 $86.35   10.774%   $95.6533   $95.65   $95.65   $95.70  
  Purchase #2 $203.99   10.799%   $226.0189   $226.02   $226.00   $226.00  
  Purchase #3 $233.32   10.197%   $257.1116   $257.11   $257.10   $257.10  
  Purchase #4 $84.83   3.671%   $87.9441   $87.94   $87.95   $87.90  
  Purchase #5 $63.83   3.425%   $66.0162   $66.02   $66.00   $66.00  
  Purchase #6 $85.36   9.439%   $93.4171   $93.42   $93.40   $93.40  
  Purchase #7 $179.34   4.104%   $186.7001   $186.70   $186.70   $186.70  
  7 purchase totals = $937.02       $1,012.8613   $1,012.86   $1,012.80   $1,012.80