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 $192.54   9.445%   $210.7254   $210.73   $210.75   $210.70  
  Purchase #2 $196.80   13.749%   $223.858   $223.86   $223.85   $223.90  
  Purchase #3 $65.26   6.682%   $69.6207   $69.62   $69.60   $69.60  
  Purchase #4 $203.47   7.858%   $219.4587   $219.46   $219.45   $219.50  
  Purchase #5 $249.79   7.370%   $268.1995   $268.20   $268.20   $268.20  
  Purchase #6 $160.62   8.819%   $174.7851   $174.79   $174.80   $174.80  
  Purchase #7 $193.59   11.724%   $216.2865   $216.29   $216.30   $216.30  
  7 purchase totals = $1,262.07       $1,382.9339   $1,382.95   $1,382.95   $1,383.00