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 $22.90   13.310%   $25.948   $25.95   $25.95   $25.90  
  Purchase #2 $70.94   4.421%   $74.0763   $74.08   $74.10   $74.10  
  Purchase #3 $56.92   6.507%   $60.6238   $60.62   $60.60   $60.60  
  Purchase #4 $94.67   12.346%   $106.358   $106.36   $106.35   $106.40  
  Purchase #5 $58.56   9.708%   $64.245   $64.25   $64.25   $64.20  
  Purchase #6 $9.67   8.311%   $10.4737   $10.47   $10.45   $10.50  
  Purchase #7 $103.76   3.676%   $107.5742   $107.57   $107.55   $107.60  
  7 purchase totals = $417.42       $449.2990   $449.30   $449.25   $449.30