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 $216.67   11.669%   $241.9532   $241.95   $241.95   $242.00  
  Purchase #2 $162.38   7.199%   $174.0697   $174.07   $174.05   $174.10  
  Purchase #3 $53.82   5.855%   $56.9712   $56.97   $56.95   $57.00  
  Purchase #4 $157.75   9.706%   $173.0612   $173.06   $173.05   $173.10  
  Purchase #5 $109.68   9.225%   $119.798   $119.80   $119.80   $119.80  
  Purchase #6 $176.27   7.767%   $189.9609   $189.96   $189.95   $190.00  
  Purchase #7 $185.88   6.362%   $197.7057   $197.71   $197.70   $197.70  
  7 purchase totals = $1,062.45       $1,153.5199   $1,153.52   $1,153.45   $1,153.70