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 $241.91   10.503%   $267.3178   $267.32   $267.30   $267.30  
  Purchase #2 $239.65   8.802%   $260.744   $260.74   $260.75   $260.70  
  Purchase #3 $10.27   8.396%   $11.1323   $11.13   $11.15   $11.10  
  Purchase #4 $57.58   3.513%   $59.6028   $59.60   $59.60   $59.60  
  Purchase #5 $31.27   11.837%   $34.9714   $34.97   $34.95   $35.00  
  Purchase #6 $196.54   3.751%   $203.9122   $203.91   $203.90   $203.90  
  Purchase #7 $51.51   11.411%   $57.3878   $57.39   $57.40   $57.40  
  7 purchase totals = $828.73       $895.0683   $895.06   $895.05   $895.00