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 $133.26   10.763%   $147.6028   $147.60   $147.60   $147.60  
  Purchase #2 $157.41   3.173%   $162.4046   $162.40   $162.40   $162.40  
  Purchase #3 $62.78   3.449%   $64.9453   $64.95   $64.95   $64.90  
  Purchase #4 $72.49   9.637%   $79.4759   $79.48   $79.50   $79.50  
  Purchase #5 $183.98   9.199%   $200.9043   $200.90   $200.90   $200.90  
  Purchase #6 $59.99   12.312%   $67.376   $67.38   $67.40   $67.40  
  Purchase #7 $36.64   5.287%   $38.5772   $38.58   $38.60   $38.60  
  7 purchase totals = $706.55       $761.2861   $761.29   $761.35   $761.30