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 $23.59   10.863%   $26.1526   $26.15   $26.15   $26.20  
  Purchase #2 $239.98   8.357%   $260.0351   $260.04   $260.05   $260.00  
  Purchase #3 $120.31   3.230%   $124.196   $124.20   $124.20   $124.20  
  Purchase #4 $102.48   13.146%   $115.952   $115.95   $115.95   $116.00  
  Purchase #5 $228.76   13.810%   $260.3518   $260.35   $260.35   $260.40  
  Purchase #6 $209.77   13.473%   $238.0323   $238.03   $238.05   $238.00  
  Purchase #7 $138.54   9.154%   $151.222   $151.22   $151.20   $151.20  
  7 purchase totals = $1,063.43       $1,175.9418   $1,175.94   $1,175.95   $1,176.00