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 $216.42   7.565%   $232.7922   $232.79   $232.80   $232.80  
  Purchase #2 $169.79   7.759%   $182.964   $182.96   $182.95   $183.00  
  Purchase #3 $190.59   6.691%   $203.3424   $203.34   $203.35   $203.30  
  Purchase #4 $54.75   3.575%   $56.7073   $56.71   $56.70   $56.70  
  Purchase #5 $45.88   5.545%   $48.424   $48.42   $48.40   $48.40  
  Purchase #6 $181.74   6.605%   $193.7439   $193.74   $193.75   $193.70  
  Purchase #7 $91.54   4.774%   $95.9101   $95.91   $95.90   $95.90  
  7 purchase totals = $950.71       $1,013.8839   $1,013.87   $1,013.85   $1,013.80