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 $84.66   12.695%   $95.4076   $95.41   $95.40   $95.40  
  Purchase #2 $219.33   8.440%   $237.8415   $237.84   $237.85   $237.80  
  Purchase #3 $8.88   8.122%   $9.6012   $9.60   $9.60   $9.60  
  Purchase #4 $127.56   10.678%   $141.1809   $141.18   $141.20   $141.20  
  Purchase #5 $232.66   13.474%   $264.0086   $264.01   $264.00   $264.00  
  Purchase #6 $237.37   5.833%   $251.2158   $251.22   $251.20   $251.20  
  Purchase #7 $219.90   10.750%   $243.5393   $243.54   $243.55   $243.50  
  7 purchase totals = $1,130.36       $1,242.7949   $1,242.80   $1,242.80   $1,242.70