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 $238.41   10.242%   $262.828   $262.83   $262.85   $262.80  
  Purchase #2 $124.45   6.465%   $132.4957   $132.50   $132.50   $132.50  
  Purchase #3 $56.81   8.689%   $61.7462   $61.75   $61.75   $61.70  
  Purchase #4 $8.29   5.863%   $8.776   $8.78   $8.80   $8.80  
  Purchase #5 $244.94   10.322%   $270.2227   $270.22   $270.20   $270.20  
  Purchase #6 $246.42   5.748%   $260.5842   $260.58   $260.60   $260.60  
  Purchase #7 $112.64   11.840%   $125.9766   $125.98   $126.00   $126.00  
  7 purchase totals = $1,031.96       $1,122.6294   $1,122.64   $1,122.70   $1,122.60