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 $112.65   3.473%   $116.5623   $116.56   $116.55   $116.60  
  Purchase #2 $138.77   4.727%   $145.3297   $145.33   $145.35   $145.30  
  Purchase #3 $96.54   12.230%   $108.3468   $108.35   $108.35   $108.30  
  Purchase #4 $162.67   12.655%   $183.2559   $183.26   $183.25   $183.30  
  Purchase #5 $191.77   6.375%   $203.9953   $204.00   $204.00   $204.00  
  Purchase #6 $226.63   13.721%   $257.7259   $257.73   $257.75   $257.70  
  Purchase #7 $7.46   8.365%   $8.084   $8.08   $8.10   $8.10  
  7 purchase totals = $936.49       $1,023.2999   $1,023.31   $1,023.35   $1,023.30