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 $116.29   7.797%   $125.3571   $125.36   $125.35   $125.40  
  Purchase #2 $216.54   3.287%   $223.6577   $223.66   $223.65   $223.70  
  Purchase #3 $74.89   7.351%   $80.3952   $80.40   $80.40   $80.40  
  Purchase #4 $112.65   6.292%   $119.7379   $119.74   $119.75   $119.70  
  Purchase #5 $16.27   8.157%   $17.5971   $17.60   $17.60   $17.60  
  Purchase #6 $180.76   13.235%   $204.6836   $204.68   $204.70   $204.70  
  Purchase #7 $233.78   5.315%   $246.2054   $246.21   $246.20   $246.20  
  7 purchase totals = $951.18       $1,017.6340   $1,017.65   $1,017.65   $1,017.70