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 $193.71   6.834%   $206.9481   $206.95   $206.95   $206.90  
  Purchase #2 $210.74   10.432%   $232.7244   $232.72   $232.70   $232.70  
  Purchase #3 $187.37   8.788%   $203.8361   $203.84   $203.85   $203.80  
  Purchase #4 $171.91   12.578%   $193.5328   $193.53   $193.55   $193.50  
  Purchase #5 $173.48   11.286%   $193.059   $193.06   $193.05   $193.10  
  Purchase #6 $163.54   3.325%   $168.9777   $168.98   $169.00   $169.00  
  Purchase #7 $61.99   10.792%   $68.68   $68.68   $68.70   $68.70  
  7 purchase totals = $1,162.74       $1,267.7581   $1,267.76   $1,267.80   $1,267.70