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 $44.77   3.561%   $46.3643   $46.36   $46.35   $46.40  
  Purchase #2 $160.91   6.642%   $171.5976   $171.60   $171.60   $171.60  
  Purchase #3 $65.39   8.521%   $70.9619   $70.96   $70.95   $71.00  
  Purchase #4 $246.63   7.371%   $264.8091   $264.81   $264.80   $264.80  
  Purchase #5 $75.94   11.402%   $84.5987   $84.60   $84.60   $84.60  
  Purchase #6 $120.74   3.661%   $125.1603   $125.16   $125.15   $125.20  
  Purchase #7 $129.49   6.197%   $137.5145   $137.51   $137.50   $137.50  
  7 purchase totals = $843.87       $901.0064   $901.00   $900.95   $901.10