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 $85.42   10.625%   $94.4959   $94.50   $94.50   $94.50  
  Purchase #2 $70.95   3.589%   $73.4964   $73.50   $73.50   $73.50  
  Purchase #3 $119.70   11.393%   $133.3374   $133.34   $133.35   $133.30  
  Purchase #4 $161.89   9.307%   $176.9571   $176.96   $176.95   $177.00  
  Purchase #5 $144.61   12.451%   $162.6154   $162.62   $162.60   $162.60  
  Purchase #6 $121.74   13.357%   $138.0008   $138.00   $138.00   $138.00  
  Purchase #7 $238.58   11.643%   $266.3579   $266.36   $266.35   $266.40  
  7 purchase totals = $942.89       $1,045.2609   $1,045.28   $1,045.25   $1,045.30