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 $58.74   7.201%   $62.9699   $62.97   $62.95   $63.00  
  Purchase #2 $195.50   8.364%   $211.8516   $211.85   $211.85   $211.90  
  Purchase #3 $164.81   13.565%   $187.1665   $187.17   $187.15   $187.20  
  Purchase #4 $198.71   12.433%   $223.4156   $223.42   $223.40   $223.40  
  Purchase #5 $246.36   4.566%   $257.6088   $257.61   $257.60   $257.60  
  Purchase #6 $25.32   12.381%   $28.4549   $28.45   $28.45   $28.50  
  Purchase #7 $91.42   12.624%   $102.9609   $102.96   $102.95   $103.00  
  7 purchase totals = $980.86       $1,074.4282   $1,074.43   $1,074.35   $1,074.60