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 $216.97   8.403%   $235.202   $235.20   $235.20   $235.20  
  Purchase #2 $39.93   8.146%   $43.1827   $43.18   $43.20   $43.20  
  Purchase #3 $113.56   5.142%   $119.3993   $119.40   $119.40   $119.40  
  Purchase #4 $195.84   9.459%   $214.3645   $214.36   $214.35   $214.40  
  Purchase #5 $206.72   13.387%   $234.3936   $234.39   $234.40   $234.40  
  Purchase #6 $150.51   7.750%   $162.1745   $162.17   $162.15   $162.20  
  Purchase #7 $142.56   7.190%   $152.8101   $152.81   $152.80   $152.80  
  7 purchase totals = $1,066.09       $1,161.5267   $1,161.51   $1,161.50   $1,161.60