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 $88.29   8.337%   $95.6507   $95.65   $95.65   $95.70  
  Purchase #2 $216.61   5.156%   $227.7784   $227.78   $227.80   $227.80  
  Purchase #3 $107.89   12.405%   $121.2738   $121.27   $121.25   $121.30  
  Purchase #4 $196.84   4.338%   $205.3789   $205.38   $205.40   $205.40  
  Purchase #5 $50.99   4.691%   $53.3819   $53.38   $53.40   $53.40  
  Purchase #6 $25.58   6.775%   $27.313   $27.31   $27.30   $27.30  
  Purchase #7 $14.90   10.125%   $16.4086   $16.41   $16.40   $16.40  
  7 purchase totals = $701.10       $747.1853   $747.18   $747.20   $747.30