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 $168.69   9.620%   $184.918   $184.92   $184.90   $184.90  
  Purchase #2 $205.31   5.148%   $215.8794   $215.88   $215.90   $215.90  
  Purchase #3 $81.73   7.216%   $87.6276   $87.63   $87.65   $87.60  
  Purchase #4 $102.39   3.723%   $106.202   $106.20   $106.20   $106.20  
  Purchase #5 $11.95   13.166%   $13.5233   $13.52   $13.50   $13.50  
  Purchase #6 $238.67   10.271%   $263.1838   $263.18   $263.20   $263.20  
  Purchase #7 $144.89   13.112%   $163.888   $163.89   $163.90   $163.90  
  7 purchase totals = $953.63       $1,035.2221   $1,035.22   $1,035.25   $1,035.20