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 $87.26   11.106%   $96.9511   $96.95   $96.95   $97.00  
  Purchase #2 $147.28   8.757%   $160.1773   $160.18   $160.20   $160.20  
  Purchase #3 $17.63   8.842%   $19.1888   $19.19   $19.20   $19.20  
  Purchase #4 $178.31   12.396%   $200.4133   $200.41   $200.40   $200.40  
  Purchase #5 $135.82   9.169%   $148.2733   $148.27   $148.25   $148.30  
  Purchase #6 $116.34   4.675%   $121.7789   $121.78   $121.80   $121.80  
  Purchase #7 $131.77   11.562%   $147.0052   $147.01   $147.00   $147.00  
  7 purchase totals = $814.41       $893.7879   $893.79   $893.80   $893.90