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 $140.62   8.573%   $152.6754   $152.68   $152.70   $152.70  
  Purchase #2 $241.93   8.676%   $262.9198   $262.92   $262.90   $262.90  
  Purchase #3 $67.42   10.829%   $74.7209   $74.72   $74.70   $74.70  
  Purchase #4 $194.53   12.528%   $218.9007   $218.90   $218.90   $218.90  
  Purchase #5 $85.37   3.300%   $88.1872   $88.19   $88.20   $88.20  
  Purchase #6 $183.75   9.796%   $201.7502   $201.75   $201.75   $201.80  
  Purchase #7 $154.45   11.315%   $171.926   $171.93   $171.95   $171.90  
  7 purchase totals = $1,068.07       $1,171.0802   $1,171.09   $1,171.10   $1,171.10