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 $88.89   7.430%   $95.4945   $95.49   $95.50   $95.50  
  Purchase #2 $146.61   6.518%   $156.166   $156.17   $156.15   $156.20  
  Purchase #3 $106.91   4.392%   $111.6055   $111.61   $111.60   $111.60  
  Purchase #4 $31.36   8.162%   $33.9196   $33.92   $33.90   $33.90  
  Purchase #5 $184.59   7.624%   $198.6631   $198.66   $198.65   $198.70  
  Purchase #6 $132.82   12.741%   $149.7426   $149.74   $149.75   $149.70  
  Purchase #7 $167.26   6.405%   $177.973   $177.97   $177.95   $178.00  
  7 purchase totals = $858.44       $923.5643   $923.56   $923.50   $923.60