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 $93.96   3.364%   $97.1208   $97.12   $97.10   $97.10  
  Purchase #2 $91.65   13.169%   $103.7194   $103.72   $103.70   $103.70  
  Purchase #3 $183.71   9.256%   $200.7142   $200.71   $200.70   $200.70  
  Purchase #4 $27.26   11.114%   $30.2897   $30.29   $30.30   $30.30  
  Purchase #5 $218.90   6.856%   $233.9078   $233.91   $233.90   $233.90  
  Purchase #6 $193.32   9.304%   $211.3065   $211.31   $211.30   $211.30  
  Purchase #7 $185.99   11.363%   $207.124   $207.12   $207.10   $207.10  
  7 purchase totals = $994.79       $1,084.1824   $1,084.18   $1,084.10   $1,084.10