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 $189.44   3.466%   $196.006   $196.01   $196.00   $196.00  
  Purchase #2 $202.66   13.337%   $229.6888   $229.69   $229.70   $229.70  
  Purchase #3 $177.99   3.751%   $184.6664   $184.67   $184.65   $184.70  
  Purchase #4 $150.52   11.308%   $167.5408   $167.54   $167.55   $167.50  
  Purchase #5 $192.41   4.828%   $201.6996   $201.70   $201.70   $201.70  
  Purchase #6 $43.75   9.466%   $47.8914   $47.89   $47.90   $47.90  
  Purchase #7 $84.51   6.514%   $90.015   $90.02   $90.00   $90.00  
  7 purchase totals = $1,041.28       $1,117.5080   $1,117.52   $1,117.50   $1,117.50