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 $244.97   9.229%   $267.5783   $267.58   $267.60   $267.60  
  Purchase #2 $95.98   10.525%   $106.0819   $106.08   $106.10   $106.10  
  Purchase #3 $176.27   13.700%   $200.419   $200.42   $200.40   $200.40  
  Purchase #4 $242.55   9.477%   $265.5365   $265.54   $265.55   $265.50  
  Purchase #5 $240.35   7.230%   $257.7273   $257.73   $257.75   $257.70  
  Purchase #6 $204.59   6.611%   $218.1154   $218.12   $218.10   $218.10  
  Purchase #7 $68.65   3.263%   $70.89   $70.89   $70.90   $70.90  
  7 purchase totals = $1,273.36       $1,386.3484   $1,386.36   $1,386.40   $1,386.30