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 $101.60   12.187%   $113.982   $113.98   $114.00   $114.00  
  Purchase #2 $25.58   13.368%   $28.9995   $29.00   $29.00   $29.00  
  Purchase #3 $141.38   4.111%   $147.1921   $147.19   $147.20   $147.20  
  Purchase #4 $58.42   11.677%   $65.2417   $65.24   $65.25   $65.20  
  Purchase #5 $230.88   3.125%   $238.095   $238.10   $238.10   $238.10  
  Purchase #6 $234.70   13.137%   $265.5325   $265.53   $265.55   $265.50  
  Purchase #7 $150.41   4.638%   $157.386   $157.39   $157.40   $157.40  
  7 purchase totals = $942.97       $1,016.4288   $1,016.43   $1,016.50   $1,016.40