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 $85.35   11.148%   $94.8648   $94.86   $94.85   $94.90  
  Purchase #2 $219.44   8.166%   $237.3595   $237.36   $237.35   $237.40  
  Purchase #3 $210.42   12.742%   $237.2317   $237.23   $237.25   $237.20  
  Purchase #4 $85.44   3.361%   $88.3116   $88.31   $88.30   $88.30  
  Purchase #5 $226.54   4.469%   $236.6641   $236.66   $236.65   $236.70  
  Purchase #6 $156.74   3.778%   $162.6616   $162.66   $162.65   $162.70  
  Purchase #7 $187.98   13.731%   $213.7915   $213.79   $213.80   $213.80  
  7 purchase totals = $1,171.91       $1,270.8848   $1,270.87   $1,270.85   $1,271.00