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 $243.37   7.652%   $261.9927   $261.99   $262.00   $262.00  
  Purchase #2 $169.39   12.336%   $190.286   $190.29   $190.30   $190.30  
  Purchase #3 $36.67   8.171%   $39.6663   $39.67   $39.65   $39.70  
  Purchase #4 $194.57   12.132%   $218.1752   $218.18   $218.20   $218.20  
  Purchase #5 $209.37   11.241%   $232.9053   $232.91   $232.90   $232.90  
  Purchase #6 $225.27   10.670%   $249.3063   $249.31   $249.30   $249.30  
  Purchase #7 $194.30   3.482%   $201.0655   $201.07   $201.05   $201.10  
  7 purchase totals = $1,272.94       $1,393.3973   $1,393.42   $1,393.40   $1,393.50