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 $41.83   7.463%   $44.9518   $44.95   $44.95   $45.00  
  Purchase #2 $195.73   12.273%   $219.7519   $219.75   $219.75   $219.80  
  Purchase #3 $44.75   6.782%   $47.7849   $47.78   $47.80   $47.80  
  Purchase #4 $177.73   9.443%   $194.513   $194.51   $194.50   $194.50  
  Purchase #5 $7.35   12.499%   $8.2687   $8.27   $8.25   $8.30  
  Purchase #6 $234.60   5.709%   $247.9933   $247.99   $248.00   $248.00  
  Purchase #7 $96.47   8.234%   $104.4133   $104.41   $104.40   $104.40  
  7 purchase totals = $798.46       $867.6769   $867.66   $867.65   $867.80