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 $108.73   5.488%   $114.6971   $114.70   $114.70   $114.70  
  Purchase #2 $239.32   11.580%   $267.0333   $267.03   $267.05   $267.00  
  Purchase #3 $15.67   5.454%   $16.5246   $16.52   $16.50   $16.50  
  Purchase #4 $36.99   13.282%   $41.903   $41.90   $41.90   $41.90  
  Purchase #5 $196.39   6.493%   $209.1416   $209.14   $209.15   $209.10  
  Purchase #6 $48.97   12.428%   $55.056   $55.06   $55.05   $55.10  
  Purchase #7 $95.62   12.519%   $107.5907   $107.59   $107.60   $107.60  
  7 purchase totals = $741.69       $811.9463   $811.94   $811.95   $811.90