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 $243.99   7.348%   $261.9184   $261.92   $261.90   $261.90  
  Purchase #2 $162.83   8.689%   $176.9783   $176.98   $177.00   $177.00  
  Purchase #3 $43.29   4.191%   $45.1043   $45.10   $45.10   $45.10  
  Purchase #4 $98.27   12.551%   $110.6039   $110.60   $110.60   $110.60  
  Purchase #5 $126.31   4.685%   $132.2276   $132.23   $132.25   $132.20  
  Purchase #6 $201.99   11.581%   $225.3825   $225.38   $225.40   $225.40  
  Purchase #7 $187.58   11.573%   $209.2886   $209.29   $209.30   $209.30  
  7 purchase totals = $1,064.26       $1,161.5036   $1,161.50   $1,161.55   $1,161.50