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 $241.29   11.560%   $269.1831   $269.18   $269.20   $269.20  
  Purchase #2 $238.72   5.814%   $252.5992   $252.60   $252.60   $252.60  
  Purchase #3 $194.62   4.165%   $202.7259   $202.73   $202.75   $202.70  
  Purchase #4 $185.69   4.239%   $193.5614   $193.56   $193.55   $193.60  
  Purchase #5 $159.73   12.236%   $179.2746   $179.27   $179.25   $179.30  
  Purchase #6 $45.37   12.329%   $50.9637   $50.96   $50.95   $51.00  
  Purchase #7 $198.80   8.690%   $216.0757   $216.08   $216.10   $216.10  
  7 purchase totals = $1,264.22       $1,364.3836   $1,364.38   $1,364.40   $1,364.50