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 $81.43   6.532%   $86.749   $86.75   $86.75   $86.70  
  Purchase #2 $195.93   7.631%   $210.8814   $210.88   $210.90   $210.90  
  Purchase #3 $92.42   9.825%   $101.5003   $101.50   $101.50   $101.50  
  Purchase #4 $132.92   7.410%   $142.7694   $142.77   $142.75   $142.80  
  Purchase #5 $243.92   8.205%   $263.9336   $263.93   $263.95   $263.90  
  Purchase #6 $80.72   8.736%   $87.7717   $87.77   $87.75   $87.80  
  Purchase #7 $232.65   7.514%   $250.1313   $250.13   $250.15   $250.10  
  7 purchase totals = $1,059.99       $1,143.7367   $1,143.73   $1,143.75   $1,143.70