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 $112.62   9.394%   $123.1995   $123.20   $123.20   $123.20  
  Purchase #2 $67.94   7.773%   $73.221   $73.22   $73.20   $73.20  
  Purchase #3 $141.27   13.790%   $160.7511   $160.75   $160.75   $160.80  
  Purchase #4 $186.51   12.373%   $209.5869   $209.59   $209.60   $209.60  
  Purchase #5 $205.60   5.144%   $216.1761   $216.18   $216.20   $216.20  
  Purchase #6 $135.98   10.720%   $150.5571   $150.56   $150.55   $150.60  
  Purchase #7 $218.63   11.106%   $242.911   $242.91   $242.90   $242.90  
  7 purchase totals = $1,068.55       $1,176.4027   $1,176.41   $1,176.40   $1,176.50