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 $88.63   9.388%   $96.9506   $96.95   $96.95   $97.00  
  Purchase #2 $213.28   12.259%   $239.426   $239.43   $239.45   $239.40  
  Purchase #3 $15.37   7.256%   $16.4852   $16.49   $16.50   $16.50  
  Purchase #4 $212.25   6.821%   $226.7276   $226.73   $226.75   $226.70  
  Purchase #5 $71.85   12.624%   $80.9203   $80.92   $80.90   $80.90  
  Purchase #6 $61.28   12.560%   $68.9768   $68.98   $69.00   $69.00  
  Purchase #7 $90.35   13.716%   $102.7424   $102.74   $102.75   $102.70  
  7 purchase totals = $753.01       $832.2289   $832.24   $832.30   $832.20