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 $68.44   11.495%   $76.3072   $76.31   $76.30   $76.30  
  Purchase #2 $174.78   11.832%   $195.46   $195.46   $195.45   $195.50  
  Purchase #3 $99.85   8.355%   $108.1925   $108.19   $108.20   $108.20  
  Purchase #4 $66.48   9.496%   $72.7929   $72.79   $72.80   $72.80  
  Purchase #5 $151.92   10.799%   $168.3258   $168.33   $168.35   $168.30  
  Purchase #6 $118.42   13.205%   $134.0574   $134.06   $134.05   $134.10  
  Purchase #7 $188.54   9.743%   $206.9095   $206.91   $206.90   $206.90  
  7 purchase totals = $868.43       $962.0453   $962.05   $962.05   $962.10