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 $119.44   4.669%   $125.0167   $125.02   $125.00   $125.00  
  Purchase #2 $107.85   7.319%   $115.7435   $115.74   $115.75   $115.70  
  Purchase #3 $204.80   11.419%   $228.1861   $228.19   $228.20   $228.20  
  Purchase #4 $186.56   4.247%   $194.4832   $194.48   $194.50   $194.50  
  Purchase #5 $110.62   5.245%   $116.422   $116.42   $116.40   $116.40  
  Purchase #6 $162.90   10.112%   $179.3724   $179.37   $179.35   $179.40  
  Purchase #7 $53.50   5.752%   $56.5773   $56.58   $56.60   $56.60  
  7 purchase totals = $945.67       $1,015.8012   $1,015.80   $1,015.80   $1,015.80