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 $241.46   11.712%   $269.7398   $269.74   $269.75   $269.70  
  Purchase #2 $151.75   9.372%   $165.972   $165.97   $165.95   $166.00  
  Purchase #3 $148.46   4.376%   $154.9566   $154.96   $154.95   $155.00  
  Purchase #4 $55.64   11.320%   $61.9384   $61.94   $61.95   $61.90  
  Purchase #5 $220.94   5.550%   $233.2022   $233.20   $233.20   $233.20  
  Purchase #6 $113.46   5.817%   $120.06   $120.06   $120.05   $120.10  
  Purchase #7 $149.69   8.237%   $162.02   $162.02   $162.00   $162.00  
  7 purchase totals = $1,081.40       $1,167.8890   $1,167.89   $1,167.85   $1,167.90