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 $202.34   6.761%   $216.0202   $216.02   $216.00   $216.00  
  Purchase #2 $14.61   7.814%   $15.7516   $15.75   $15.75   $15.80  
  Purchase #3 $126.97   5.275%   $133.6677   $133.67   $133.65   $133.70  
  Purchase #4 $191.73   3.112%   $197.6966   $197.70   $197.70   $197.70  
  Purchase #5 $248.84   4.439%   $259.886   $259.89   $259.90   $259.90  
  Purchase #6 $97.63   6.310%   $103.7905   $103.79   $103.80   $103.80  
  Purchase #7 $17.55   3.591%   $18.1802   $18.18   $18.20   $18.20  
  7 purchase totals = $899.67       $944.9928   $945.00   $945.00   $945.10