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 $111.79   5.179%   $117.5796   $117.58   $117.60   $117.60  
  Purchase #2 $153.93   8.526%   $167.0541   $167.05   $167.05   $167.10  
  Purchase #3 $169.81   10.635%   $187.8693   $187.87   $187.85   $187.90  
  Purchase #4 $64.45   5.732%   $68.1443   $68.14   $68.15   $68.10  
  Purchase #5 $154.91   5.766%   $163.8421   $163.84   $163.85   $163.80  
  Purchase #6 $109.41   5.855%   $115.816   $115.82   $115.80   $115.80  
  Purchase #7 $206.74   3.753%   $214.499   $214.50   $214.50   $214.50  
  7 purchase totals = $971.04       $1,034.8044   $1,034.80   $1,034.80   $1,034.80