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 $69.73   5.493%   $73.5603   $73.56   $73.55   $73.60  
  Purchase #2 $248.59   4.234%   $259.1153   $259.12   $259.10   $259.10  
  Purchase #3 $102.36   4.113%   $106.5701   $106.57   $106.55   $106.60  
  Purchase #4 $119.79   6.251%   $127.2781   $127.28   $127.30   $127.30  
  Purchase #5 $179.77   12.634%   $202.4821   $202.48   $202.50   $202.50  
  Purchase #6 $188.97   5.446%   $199.2613   $199.26   $199.25   $199.30  
  Purchase #7 $37.49   13.321%   $42.484   $42.48   $42.50   $42.50  
  7 purchase totals = $946.70       $1,010.7512   $1,010.75   $1,010.75   $1,010.90