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 $67.53   5.136%   $70.9983   $71.00   $71.00   $71.00  
  Purchase #2 $194.60   6.599%   $207.4417   $207.44   $207.45   $207.40  
  Purchase #3 $164.54   13.523%   $186.7907   $186.79   $186.80   $186.80  
  Purchase #4 $59.58   6.370%   $63.3752   $63.38   $63.40   $63.40  
  Purchase #5 $232.59   4.863%   $243.9009   $243.90   $243.90   $243.90  
  Purchase #6 $219.34   12.269%   $246.2508   $246.25   $246.25   $246.30  
  Purchase #7 $75.40   3.640%   $78.1446   $78.14   $78.15   $78.10  
  7 purchase totals = $1,013.58       $1,096.9022   $1,096.90   $1,096.95   $1,096.90