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 $242.70   8.410%   $263.1111   $263.11   $263.10   $263.10  
  Purchase #2 $82.41   3.221%   $85.0644   $85.06   $85.05   $85.10  
  Purchase #3 $78.92   9.232%   $86.2059   $86.21   $86.20   $86.20  
  Purchase #4 $193.57   6.805%   $206.7424   $206.74   $206.75   $206.70  
  Purchase #5 $41.40   7.431%   $44.4764   $44.48   $44.50   $44.50  
  Purchase #6 $174.80   12.148%   $196.0347   $196.03   $196.05   $196.00  
  Purchase #7 $152.96   6.544%   $162.9697   $162.97   $162.95   $163.00  
  7 purchase totals = $966.76       $1,044.6046   $1,044.60   $1,044.60   $1,044.60