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 $136.72   11.154%   $151.9697   $151.97   $151.95   $152.00  
  Purchase #2 $239.80   5.387%   $252.718   $252.72   $252.70   $252.70  
  Purchase #3 $206.90   6.530%   $220.4106   $220.41   $220.40   $220.40  
  Purchase #4 $64.46   3.322%   $66.6014   $66.60   $66.60   $66.60  
  Purchase #5 $60.56   5.684%   $64.0022   $64.00   $64.00   $64.00  
  Purchase #6 $55.92   11.354%   $62.2692   $62.27   $62.25   $62.30  
  Purchase #7 $208.57   4.183%   $217.2945   $217.29   $217.30   $217.30  
  7 purchase totals = $972.93       $1,035.2656   $1,035.26   $1,035.20   $1,035.30