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 $210.83   10.848%   $233.7008   $233.70   $233.70   $233.70  
  Purchase #2 $108.39   6.200%   $115.1102   $115.11   $115.10   $115.10  
  Purchase #3 $163.92   7.177%   $175.6845   $175.68   $175.70   $175.70  
  Purchase #4 $163.58   5.759%   $173.0006   $173.00   $173.00   $173.00  
  Purchase #5 $22.44   13.150%   $25.3909   $25.39   $25.40   $25.40  
  Purchase #6 $156.65   8.123%   $169.3747   $169.37   $169.35   $169.40  
  Purchase #7 $57.25   7.746%   $61.6846   $61.68   $61.70   $61.70  
  7 purchase totals = $883.06       $953.9463   $953.93   $953.95   $954.00