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 $172.64   7.188%   $185.0494   $185.05   $185.05   $185.00  
  Purchase #2 $46.97   4.334%   $49.0057   $49.01   $49.00   $49.00  
  Purchase #3 $228.91   4.870%   $240.0579   $240.06   $240.05   $240.10  
  Purchase #4 $210.62   11.355%   $234.5359   $234.54   $234.55   $234.50  
  Purchase #5 $62.42   8.599%   $67.7875   $67.79   $67.80   $67.80  
  Purchase #6 $133.38   7.600%   $143.5169   $143.52   $143.50   $143.50  
  Purchase #7 $108.65   5.573%   $114.7051   $114.71   $114.70   $114.70  
  7 purchase totals = $963.59       $1,034.6584   $1,034.68   $1,034.65   $1,034.60