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 $65.67   12.636%   $73.9681   $73.97   $73.95   $74.00  
  Purchase #2 $248.44   6.601%   $264.8395   $264.84   $264.85   $264.80  
  Purchase #3 $18.38   3.419%   $19.0084   $19.01   $19.00   $19.00  
  Purchase #4 $56.67   9.304%   $61.9426   $61.94   $61.95   $61.90  
  Purchase #5 $108.62   4.633%   $113.6524   $113.65   $113.65   $113.70  
  Purchase #6 $224.37   7.144%   $240.399   $240.40   $240.40   $240.40  
  Purchase #7 $107.70   12.665%   $121.3402   $121.34   $121.35   $121.30  
  7 purchase totals = $829.85       $895.1502   $895.15   $895.15   $895.10