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 $53.60   13.510%   $60.8414   $60.84   $60.85   $60.80  
  Purchase #2 $76.73   11.673%   $85.6867   $85.69   $85.70   $85.70  
  Purchase #3 $166.25   8.873%   $181.0014   $181.00   $181.00   $181.00  
  Purchase #4 $125.49   10.559%   $138.7405   $138.74   $138.75   $138.70  
  Purchase #5 $201.63   10.272%   $222.3414   $222.34   $222.35   $222.30  
  Purchase #6 $143.79   5.398%   $151.5518   $151.55   $151.55   $151.60  
  Purchase #7 $200.80   11.297%   $223.4844   $223.48   $223.50   $223.50  
  7 purchase totals = $968.29       $1,063.6476   $1,063.64   $1,063.70   $1,063.60