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 $184.42   6.246%   $195.9389   $195.94   $195.95   $195.90  
  Purchase #2 $31.86   7.149%   $34.1377   $34.14   $34.15   $34.10  
  Purchase #3 $247.70   13.759%   $281.781   $281.78   $281.80   $281.80  
  Purchase #4 $248.88   12.567%   $280.1567   $280.16   $280.15   $280.20  
  Purchase #5 $157.55   6.165%   $167.263   $167.26   $167.25   $167.30  
  Purchase #6 $67.52   11.408%   $75.2227   $75.22   $75.20   $75.20  
  Purchase #7 $231.92   3.148%   $239.2208   $239.22   $239.20   $239.20  
  7 purchase totals = $1,169.85       $1,273.7208   $1,273.72   $1,273.70   $1,273.70