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 $65.95   13.783%   $75.0399   $75.04   $75.05   $75.00  
  Purchase #2 $187.64   4.168%   $195.4608   $195.46   $195.45   $195.50  
  Purchase #3 $44.71   13.349%   $50.6783   $50.68   $50.70   $50.70  
  Purchase #4 $243.91   4.550%   $255.0079   $255.01   $255.00   $255.00  
  Purchase #5 $17.30   13.492%   $19.6341   $19.63   $19.65   $19.60  
  Purchase #6 $160.85   10.291%   $177.4031   $177.40   $177.40   $177.40  
  Purchase #7 $216.50   10.117%   $238.4033   $238.40   $238.40   $238.40  
  7 purchase totals = $936.86       $1,011.6274   $1,011.62   $1,011.65   $1,011.60