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 $113.95   4.464%   $119.0367   $119.04   $119.05   $119.00  
  Purchase #2 $240.50   9.605%   $263.6   $263.60   $263.60   $263.60  
  Purchase #3 $90.49   7.427%   $97.2107   $97.21   $97.20   $97.20  
  Purchase #4 $172.67   9.653%   $189.3378   $189.34   $189.35   $189.30  
  Purchase #5 $27.84   8.717%   $30.2668   $30.27   $30.25   $30.30  
  Purchase #6 $152.91   7.381%   $164.1963   $164.20   $164.20   $164.20  
  Purchase #7 $184.70   9.535%   $202.3111   $202.31   $202.30   $202.30  
  7 purchase totals = $983.06       $1,065.9594   $1,065.97   $1,065.95   $1,065.90