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 $72.59   3.557%   $75.172   $75.17   $75.15   $75.20  
  Purchase #2 $240.52   7.634%   $258.8813   $258.88   $258.90   $258.90  
  Purchase #3 $47.38   4.204%   $49.3719   $49.37   $49.35   $49.40  
  Purchase #4 $161.88   8.610%   $175.8179   $175.82   $175.80   $175.80  
  Purchase #5 $123.37   11.818%   $137.9499   $137.95   $137.95   $137.90  
  Purchase #6 $109.61   3.689%   $113.6535   $113.65   $113.65   $113.70  
  Purchase #7 $244.27   8.420%   $264.8375   $264.84   $264.85   $264.80  
  7 purchase totals = $999.62       $1,075.6840   $1,075.68   $1,075.65   $1,075.70