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 $69.54   7.388%   $74.6776   $74.68   $74.70   $74.70  
  Purchase #2 $210.56   10.636%   $232.9552   $232.96   $232.95   $233.00  
  Purchase #3 $161.67   8.588%   $175.5542   $175.55   $175.55   $175.60  
  Purchase #4 $89.91   3.444%   $93.0065   $93.01   $93.00   $93.00  
  Purchase #5 $115.57   4.804%   $121.122   $121.12   $121.10   $121.10  
  Purchase #6 $236.78   11.417%   $263.8132   $263.81   $263.80   $263.80  
  Purchase #7 $82.31   12.295%   $92.43   $92.43   $92.45   $92.40  
  7 purchase totals = $966.34       $1,053.5587   $1,053.56   $1,053.55   $1,053.60