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 $246.45   11.133%   $273.8873   $273.89   $273.90   $273.90  
  Purchase #2 $42.67   4.495%   $44.588   $44.59   $44.60   $44.60  
  Purchase #3 $161.90   11.867%   $181.1127   $181.11   $181.10   $181.10  
  Purchase #4 $62.85   6.126%   $66.7002   $66.70   $66.70   $66.70  
  Purchase #5 $121.95   7.394%   $130.967   $130.97   $130.95   $131.00  
  Purchase #6 $239.47   10.287%   $264.1043   $264.10   $264.10   $264.10  
  Purchase #7 $79.90   8.445%   $86.6476   $86.65   $86.65   $86.60  
  7 purchase totals = $955.19       $1,048.0071   $1,048.01   $1,048.00   $1,048.00