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 $158.28   10.354%   $174.6683   $174.67   $174.65   $174.70  
  Purchase #2 $159.44   5.109%   $167.5858   $167.59   $167.60   $167.60  
  Purchase #3 $113.68   12.360%   $127.7308   $127.73   $127.75   $127.70  
  Purchase #4 $246.72   12.272%   $276.9975   $277.00   $277.00   $277.00  
  Purchase #5 $173.68   11.675%   $193.9571   $193.96   $193.95   $194.00  
  Purchase #6 $169.46   12.286%   $190.2799   $190.28   $190.30   $190.30  
  Purchase #7 $57.37   11.129%   $63.7547   $63.75   $63.75   $63.80  
  7 purchase totals = $1,078.63       $1,194.9741   $1,194.98   $1,195.00   $1,195.10