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 $59.65   10.224%   $65.7486   $65.75   $65.75   $65.70  
  Purchase #2 $203.90   11.221%   $226.7796   $226.78   $226.80   $226.80  
  Purchase #3 $45.47   11.168%   $50.5481   $50.55   $50.55   $50.50  
  Purchase #4 $202.70   4.660%   $212.1458   $212.15   $212.15   $212.10  
  Purchase #5 $165.41   10.558%   $182.874   $182.87   $182.85   $182.90  
  Purchase #6 $96.58   5.674%   $102.0599   $102.06   $102.05   $102.10  
  Purchase #7 $247.65   3.705%   $256.8254   $256.83   $256.85   $256.80  
  7 purchase totals = $1,021.36       $1,096.9814   $1,096.99   $1,097.00   $1,096.90