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 $201.65   7.476%   $216.7254   $216.73   $216.75   $216.70  
  Purchase #2 $163.77   9.828%   $179.8653   $179.87   $179.85   $179.90  
  Purchase #3 $156.53   9.255%   $171.0169   $171.02   $171.00   $171.00  
  Purchase #4 $225.67   8.138%   $244.035   $244.04   $244.05   $244.00  
  Purchase #5 $180.77   13.311%   $204.8323   $204.83   $204.85   $204.80  
  Purchase #6 $148.57   3.436%   $153.6749   $153.67   $153.65   $153.70  
  Purchase #7 $81.84   13.476%   $92.8688   $92.87   $92.85   $92.90  
  7 purchase totals = $1,158.80       $1,263.0186   $1,263.03   $1,263.00   $1,263.00