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 $109.94   8.199%   $118.954   $118.95   $118.95   $119.00  
  Purchase #2 $22.72   4.255%   $23.6867   $23.69   $23.70   $23.70  
  Purchase #3 $113.95   3.282%   $117.6898   $117.69   $117.70   $117.70  
  Purchase #4 $201.97   7.654%   $217.4288   $217.43   $217.45   $217.40  
  Purchase #5 $241.72   4.298%   $252.1091   $252.11   $252.10   $252.10  
  Purchase #6 $93.83   3.811%   $97.4059   $97.41   $97.40   $97.40  
  Purchase #7 $230.84   6.127%   $244.9836   $244.98   $245.00   $245.00  
  7 purchase totals = $1,014.97       $1,072.2579   $1,072.26   $1,072.30   $1,072.30