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 $225.66   4.432%   $235.6613   $235.66   $235.65   $235.70  
  Purchase #2 $126.58   4.741%   $132.5812   $132.58   $132.60   $132.60  
  Purchase #3 $85.40   11.212%   $94.975   $94.98   $95.00   $95.00  
  Purchase #4 $35.56   11.851%   $39.7742   $39.77   $39.75   $39.80  
  Purchase #5 $204.31   4.518%   $213.5407   $213.54   $213.55   $213.50  
  Purchase #6 $15.72   5.464%   $16.5789   $16.58   $16.60   $16.60  
  Purchase #7 $8.46   3.320%   $8.7409   $8.74   $8.75   $8.70  
  7 purchase totals = $701.69       $741.8522   $741.85   $741.90   $741.90