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 $141.35   3.839%   $146.7764   $146.78   $146.80   $146.80  
  Purchase #2 $209.67   3.809%   $217.6563   $217.66   $217.65   $217.70  
  Purchase #3 $211.45   5.860%   $223.841   $223.84   $223.85   $223.80  
  Purchase #4 $165.28   11.129%   $183.674   $183.67   $183.65   $183.70  
  Purchase #5 $135.90   10.157%   $149.7034   $149.70   $149.70   $149.70  
  Purchase #6 $150.27   4.614%   $157.2035   $157.20   $157.20   $157.20  
  Purchase #7 $82.61   6.647%   $88.1011   $88.10   $88.10   $88.10  
  7 purchase totals = $1,096.53       $1,166.9557   $1,166.95   $1,166.95   $1,167.00