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 $167.60   5.653%   $177.0744   $177.07   $177.05   $177.10  
  Purchase #2 $179.49   13.757%   $204.1824   $204.18   $204.20   $204.20  
  Purchase #3 $65.36   9.721%   $71.7136   $71.71   $71.70   $71.70  
  Purchase #4 $150.59   11.870%   $168.465   $168.47   $168.45   $168.50  
  Purchase #5 $168.47   8.691%   $183.1117   $183.11   $183.10   $183.10  
  Purchase #6 $46.68   7.598%   $50.2267   $50.23   $50.25   $50.20  
  Purchase #7 $169.30   6.774%   $180.7684   $180.77   $180.75   $180.80  
  7 purchase totals = $947.49       $1,035.5422   $1,035.54   $1,035.50   $1,035.60