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 $42.47   12.136%   $47.6242   $47.62   $47.60   $47.60  
  Purchase #2 $130.92   8.234%   $141.7   $141.70   $141.70   $141.70  
  Purchase #3 $133.64   11.163%   $148.5582   $148.56   $148.55   $148.60  
  Purchase #4 $161.56   3.244%   $166.801   $166.80   $166.80   $166.80  
  Purchase #5 $22.69   10.454%   $25.062   $25.06   $25.05   $25.10  
  Purchase #6 $80.52   13.607%   $91.4764   $91.48   $91.50   $91.50  
  Purchase #7 $105.91   9.317%   $115.7776   $115.78   $115.80   $115.80  
  7 purchase totals = $677.71       $736.9994   $737.00   $737.00   $737.10