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 $244.98   9.217%   $267.5598   $267.56   $267.55   $267.60  
  Purchase #2 $6.95   3.517%   $7.1944   $7.19   $7.20   $7.20  
  Purchase #3 $236.42   4.814%   $247.8013   $247.80   $247.80   $247.80  
  Purchase #4 $156.54   13.357%   $177.449   $177.45   $177.45   $177.40  
  Purchase #5 $37.38   5.567%   $39.4609   $39.46   $39.45   $39.50  
  Purchase #6 $147.80   12.680%   $166.541   $166.54   $166.55   $166.50  
  Purchase #7 $235.84   4.660%   $246.8301   $246.83   $246.85   $246.80  
  7 purchase totals = $1,065.91       $1,152.8365   $1,152.83   $1,152.85   $1,152.80