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 $84.36   12.818%   $95.1733   $95.17   $95.15   $95.20  
  Purchase #2 $220.90   13.639%   $251.0286   $251.03   $251.05   $251.00  
  Purchase #3 $88.96   5.361%   $93.7291   $93.73   $93.75   $93.70  
  Purchase #4 $201.88   10.753%   $223.5882   $223.59   $223.60   $223.60  
  Purchase #5 $184.85   13.697%   $210.1689   $210.17   $210.15   $210.20  
  Purchase #6 $225.76   6.500%   $240.4344   $240.43   $240.45   $240.40  
  Purchase #7 $214.50   8.857%   $233.4983   $233.50   $233.50   $233.50  
  7 purchase totals = $1,221.21       $1,347.6208   $1,347.62   $1,347.65   $1,347.60