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 $206.51   13.786%   $234.9795   $234.98   $235.00   $235.00  
  Purchase #2 $165.80   9.332%   $181.2725   $181.27   $181.25   $181.30  
  Purchase #3 $196.85   9.842%   $216.224   $216.22   $216.20   $216.20  
  Purchase #4 $69.35   3.607%   $71.8515   $71.85   $71.85   $71.90  
  Purchase #5 $149.69   8.782%   $162.8358   $162.84   $162.85   $162.80  
  Purchase #6 $144.87   13.153%   $163.9248   $163.92   $163.90   $163.90  
  Purchase #7 $113.75   7.576%   $122.3677   $122.37   $122.35   $122.40  
  7 purchase totals = $1,046.82       $1,153.4558   $1,153.45   $1,153.40   $1,153.50