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 $71.56   3.616%   $74.1476   $74.15   $74.15   $74.10  
  Purchase #2 $117.44   10.468%   $129.7336   $129.73   $129.75   $129.70  
  Purchase #3 $97.94   5.167%   $103.0006   $103.00   $103.00   $103.00  
  Purchase #4 $133.90   5.794%   $141.6582   $141.66   $141.65   $141.70  
  Purchase #5 $225.60   6.750%   $240.828   $240.83   $240.85   $240.80  
  Purchase #6 $115.97   10.317%   $127.9346   $127.93   $127.95   $127.90  
  Purchase #7 $198.92   5.276%   $209.415   $209.42   $209.40   $209.40  
  7 purchase totals = $961.33       $1,026.7176   $1,026.72   $1,026.75   $1,026.60