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 $224.75   3.798%   $233.286   $233.29   $233.30   $233.30  
  Purchase #2 $228.48   12.321%   $256.631   $256.63   $256.65   $256.60  
  Purchase #3 $56.55   3.799%   $58.6983   $58.70   $58.70   $58.70  
  Purchase #4 $30.95   9.594%   $33.9193   $33.92   $33.90   $33.90  
  Purchase #5 $81.45   7.421%   $87.4944   $87.49   $87.50   $87.50  
  Purchase #6 $191.62   4.495%   $200.2333   $200.23   $200.25   $200.20  
  Purchase #7 $147.93   11.592%   $165.078   $165.08   $165.10   $165.10  
  7 purchase totals = $961.73       $1,035.3403   $1,035.34   $1,035.40   $1,035.30