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 $176.90   11.159%   $196.6403   $196.64   $196.65   $196.60  
  Purchase #2 $103.43   8.310%   $112.025   $112.03   $112.05   $112.00  
  Purchase #3 $22.42   13.237%   $25.3877   $25.39   $25.40   $25.40  
  Purchase #4 $161.91   9.805%   $177.7853   $177.79   $177.80   $177.80  
  Purchase #5 $138.33   4.790%   $144.956   $144.96   $144.95   $145.00  
  Purchase #6 $221.93   12.339%   $249.3139   $249.31   $249.30   $249.30  
  Purchase #7 $50.53   11.594%   $56.3884   $56.39   $56.40   $56.40  
  7 purchase totals = $875.45       $962.4966   $962.51   $962.55   $962.50