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 $183.40   8.722%   $199.3961   $199.40   $199.40   $199.40  
  Purchase #2 $246.47   6.178%   $261.6969   $261.70   $261.70   $261.70  
  Purchase #3 $117.96   6.499%   $125.6262   $125.63   $125.65   $125.60  
  Purchase #4 $135.52   7.280%   $145.3859   $145.39   $145.40   $145.40  
  Purchase #5 $226.62   6.330%   $240.965   $240.97   $240.95   $241.00  
  Purchase #6 $98.53   6.428%   $104.8635   $104.86   $104.85   $104.90  
  Purchase #7 $14.63   10.606%   $16.1817   $16.18   $16.20   $16.20  
  7 purchase totals = $1,023.13       $1,094.1153   $1,094.13   $1,094.15   $1,094.20