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 $63.25   10.241%   $69.7274   $69.73   $69.75   $69.70  
  Purchase #2 $207.60   9.392%   $227.0978   $227.10   $227.10   $227.10  
  Purchase #3 $110.91   4.599%   $116.0108   $116.01   $116.00   $116.00  
  Purchase #4 $153.60   10.235%   $169.321   $169.32   $169.30   $169.30  
  Purchase #5 $167.81   6.679%   $179.018   $179.02   $179.00   $179.00  
  Purchase #6 $250.81   12.714%   $282.698   $282.70   $282.70   $282.70  
  Purchase #7 $188.88   7.501%   $203.0479   $203.05   $203.05   $203.00  
  7 purchase totals = $1,142.86       $1,246.9209   $1,246.93   $1,246.90   $1,246.80