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 $151.53   10.612%   $167.6104   $167.61   $167.60   $167.60  
  Purchase #2 $176.29   11.814%   $197.1169   $197.12   $197.10   $197.10  
  Purchase #3 $123.61   6.504%   $131.6496   $131.65   $131.65   $131.60  
  Purchase #4 $30.81   13.720%   $35.0371   $35.04   $35.05   $35.00  
  Purchase #5 $201.90   11.848%   $225.8211   $225.82   $225.80   $225.80  
  Purchase #6 $184.87   3.212%   $190.808   $190.81   $190.80   $190.80  
  Purchase #7 $244.97   9.326%   $267.8159   $267.82   $267.80   $267.80  
  7 purchase totals = $1,113.98       $1,215.8590   $1,215.87   $1,215.80   $1,215.70