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 $62.75   12.368%   $70.5109   $70.51   $70.50   $70.50  
  Purchase #2 $201.91   5.455%   $212.9242   $212.92   $212.90   $212.90  
  Purchase #3 $131.86   4.320%   $137.5564   $137.56   $137.55   $137.60  
  Purchase #4 $191.37   5.770%   $202.412   $202.41   $202.40   $202.40  
  Purchase #5 $10.62   11.602%   $11.8521   $11.85   $11.85   $11.90  
  Purchase #6 $167.68   8.268%   $181.5438   $181.54   $181.55   $181.50  
  Purchase #7 $194.59   7.198%   $208.5966   $208.60   $208.60   $208.60  
  7 purchase totals = $960.78       $1,025.3960   $1,025.39   $1,025.35   $1,025.40