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 $86.36   10.765%   $95.6567   $95.66   $95.65   $95.70  
  Purchase #2 $242.39   11.308%   $269.7995   $269.80   $269.80   $269.80  
  Purchase #3 $181.87   8.665%   $197.629   $197.63   $197.65   $197.60  
  Purchase #4 $36.33   13.637%   $41.2843   $41.28   $41.30   $41.30  
  Purchase #5 $80.66   11.418%   $89.8698   $89.87   $89.85   $89.90  
  Purchase #6 $119.74   10.833%   $132.7114   $132.71   $132.70   $132.70  
  Purchase #7 $45.50   3.744%   $47.2035   $47.20   $47.20   $47.20  
  7 purchase totals = $792.85       $874.1542   $874.15   $874.15   $874.20