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 $184.83   4.535%   $193.212   $193.21   $193.20   $193.20  
  Purchase #2 $212.83   9.735%   $233.549   $233.55   $233.55   $233.50  
  Purchase #3 $102.59   3.701%   $106.3869   $106.39   $106.40   $106.40  
  Purchase #4 $52.99   7.186%   $56.7979   $56.80   $56.80   $56.80  
  Purchase #5 $207.84   3.587%   $215.2952   $215.30   $215.30   $215.30  
  Purchase #6 $150.36   4.627%   $157.3172   $157.32   $157.30   $157.30  
  Purchase #7 $66.73   7.256%   $71.5719   $71.57   $71.55   $71.60  
  7 purchase totals = $978.17       $1,034.1301   $1,034.14   $1,034.10   $1,034.10