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 $194.65   8.504%   $211.203   $211.20   $211.20   $211.20  
  Purchase #2 $63.32   6.777%   $67.6112   $67.61   $67.60   $67.60  
  Purchase #3 $100.33   6.699%   $107.0511   $107.05   $107.05   $107.10  
  Purchase #4 $92.30   10.580%   $102.0653   $102.07   $102.05   $102.10  
  Purchase #5 $219.99   8.686%   $239.0983   $239.10   $239.10   $239.10  
  Purchase #6 $49.77   9.521%   $54.5086   $54.51   $54.50   $54.50  
  Purchase #7 $87.51   5.762%   $92.5523   $92.55   $92.55   $92.60  
  7 purchase totals = $807.87       $874.0898   $874.09   $874.05   $874.20