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 $72.84   4.834%   $76.3611   $76.36   $76.35   $76.40  
  Purchase #2 $215.97   7.334%   $231.8092   $231.81   $231.80   $231.80  
  Purchase #3 $16.74   13.624%   $19.0207   $19.02   $19.00   $19.00  
  Purchase #4 $242.70   12.814%   $273.7996   $273.80   $273.80   $273.80  
  Purchase #5 $157.48   13.572%   $178.8532   $178.85   $178.85   $178.90  
  Purchase #6 $144.46   4.498%   $150.9578   $150.96   $150.95   $151.00  
  Purchase #7 $125.63   9.133%   $137.1038   $137.10   $137.10   $137.10  
  7 purchase totals = $975.82       $1,067.9054   $1,067.90   $1,067.85   $1,068.00