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 $69.84   8.740%   $75.944   $75.94   $75.95   $75.90  
  Purchase #2 $219.36   13.354%   $248.6533   $248.65   $248.65   $248.70  
  Purchase #3 $213.40   7.227%   $228.8224   $228.82   $228.80   $228.80  
  Purchase #4 $164.31   8.201%   $177.7851   $177.79   $177.80   $177.80  
  Purchase #5 $165.25   5.675%   $174.6279   $174.63   $174.65   $174.60  
  Purchase #6 $210.70   4.194%   $219.5368   $219.54   $219.55   $219.50  
  Purchase #7 $161.82   6.464%   $172.28   $172.28   $172.30   $172.30  
  7 purchase totals = $1,204.68       $1,297.6495   $1,297.65   $1,297.70   $1,297.60