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 $210.42   7.274%   $225.726   $225.73   $225.75   $225.70  
  Purchase #2 $58.95   10.590%   $65.1928   $65.19   $65.20   $65.20  
  Purchase #3 $96.25   3.526%   $99.6438   $99.64   $99.65   $99.60  
  Purchase #4 $179.91   9.677%   $197.3199   $197.32   $197.30   $197.30  
  Purchase #5 $237.29   9.654%   $260.198   $260.20   $260.20   $260.20  
  Purchase #6 $179.73   4.534%   $187.879   $187.88   $187.90   $187.90  
  Purchase #7 $214.44   6.461%   $228.295   $228.30   $228.30   $228.30  
  7 purchase totals = $1,176.99       $1,264.2545   $1,264.26   $1,264.30   $1,264.20