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 $86.62   10.526%   $95.7376   $95.74   $95.75   $95.70  
  Purchase #2 $155.88   10.747%   $172.6324   $172.63   $172.65   $172.60  
  Purchase #3 $194.36   6.216%   $206.4414   $206.44   $206.45   $206.40  
  Purchase #4 $175.76   4.780%   $184.1613   $184.16   $184.15   $184.20  
  Purchase #5 $233.65   8.702%   $253.9822   $253.98   $254.00   $254.00  
  Purchase #6 $20.64   10.691%   $22.8466   $22.85   $22.85   $22.80  
  Purchase #7 $177.83   12.456%   $199.9805   $199.98   $200.00   $200.00  
  7 purchase totals = $1,044.74       $1,135.7820   $1,135.78   $1,135.85   $1,135.70