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 $61.32   13.599%   $69.6589   $69.66   $69.65   $69.70  
  Purchase #2 $88.57   4.544%   $92.5946   $92.59   $92.60   $92.60  
  Purchase #3 $31.25   9.516%   $34.2238   $34.22   $34.20   $34.20  
  Purchase #4 $88.91   8.257%   $96.2513   $96.25   $96.25   $96.30  
  Purchase #5 $145.98   12.143%   $163.7064   $163.71   $163.70   $163.70  
  Purchase #6 $67.80   6.390%   $72.1324   $72.13   $72.15   $72.10  
  Purchase #7 $191.47   6.428%   $203.7777   $203.78   $203.80   $203.80  
  7 purchase totals = $675.30       $732.3451   $732.34   $732.35   $732.40