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 $88.35   4.498%   $92.324   $92.32   $92.30   $92.30  
  Purchase #2 $221.68   13.634%   $251.9039   $251.90   $251.90   $251.90  
  Purchase #3 $136.78   7.702%   $147.3148   $147.31   $147.30   $147.30  
  Purchase #4 $242.98   4.667%   $254.3199   $254.32   $254.30   $254.30  
  Purchase #5 $231.31   5.602%   $244.268   $244.27   $244.25   $244.30  
  Purchase #6 $181.79   6.397%   $193.4191   $193.42   $193.40   $193.40  
  Purchase #7 $176.36   3.240%   $182.0741   $182.07   $182.05   $182.10  
  7 purchase totals = $1,279.25       $1,365.6238   $1,365.61   $1,365.50   $1,365.60