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 $236.89   10.740%   $262.332   $262.33   $262.35   $262.30  
  Purchase #2 $241.26   13.636%   $274.1582   $274.16   $274.15   $274.20  
  Purchase #3 $36.65   6.770%   $39.1312   $39.13   $39.15   $39.10  
  Purchase #4 $196.37   12.507%   $220.93   $220.93   $220.95   $220.90  
  Purchase #5 $88.54   12.507%   $99.6137   $99.61   $99.60   $99.60  
  Purchase #6 $214.45   7.742%   $231.0527   $231.05   $231.05   $231.10  
  Purchase #7 $61.55   6.840%   $65.76   $65.76   $65.75   $65.80  
  7 purchase totals = $1,075.71       $1,192.9778   $1,192.97   $1,193.00   $1,193.00