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 $140.46   5.152%   $147.6965   $147.70   $147.70   $147.70  
  Purchase #2 $162.38   11.280%   $180.6965   $180.70   $180.70   $180.70  
  Purchase #3 $52.69   11.353%   $58.6719   $58.67   $58.65   $58.70  
  Purchase #4 $203.45   6.458%   $216.5888   $216.59   $216.60   $216.60  
  Purchase #5 $241.39   11.597%   $269.384   $269.38   $269.40   $269.40  
  Purchase #6 $26.89   3.131%   $27.7319   $27.73   $27.75   $27.70  
  Purchase #7 $68.39   10.526%   $75.5887   $75.59   $75.60   $75.60  
  7 purchase totals = $895.65       $976.3583   $976.36   $976.40   $976.40