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 $181.52   7.262%   $194.702   $194.70   $194.70   $194.70  
  Purchase #2 $95.58   6.295%   $101.5968   $101.60   $101.60   $101.60  
  Purchase #3 $129.66   11.239%   $144.2325   $144.23   $144.25   $144.20  
  Purchase #4 $22.89   9.680%   $25.1058   $25.11   $25.10   $25.10  
  Purchase #5 $114.70   3.331%   $118.5207   $118.52   $118.50   $118.50  
  Purchase #6 $21.54   8.842%   $23.4446   $23.44   $23.45   $23.40  
  Purchase #7 $127.90   12.799%   $144.2699   $144.27   $144.25   $144.30  
  7 purchase totals = $693.79       $751.8723   $751.87   $751.85   $751.80