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 $53.96   12.793%   $60.8631   $60.86   $60.85   $60.90  
  Purchase #2 $231.42   10.140%   $254.886   $254.89   $254.90   $254.90  
  Purchase #3 $179.45   8.492%   $194.6889   $194.69   $194.70   $194.70  
  Purchase #4 $162.97   10.389%   $179.901   $179.90   $179.90   $179.90  
  Purchase #5 $78.35   8.476%   $84.9909   $84.99   $85.00   $85.00  
  Purchase #6 $43.30   11.230%   $48.1626   $48.16   $48.15   $48.20  
  Purchase #7 $231.89   12.404%   $260.6536   $260.65   $260.65   $260.70  
  7 purchase totals = $981.34       $1,084.1461   $1,084.14   $1,084.15   $1,084.30