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 $168.51   10.743%   $186.613   $186.61   $186.60   $186.60  
  Purchase #2 $163.29   12.682%   $183.9984   $184.00   $184.00   $184.00  
  Purchase #3 $6.27   4.126%   $6.5287   $6.53   $6.55   $6.50  
  Purchase #4 $108.60   8.466%   $117.7941   $117.79   $117.80   $117.80  
  Purchase #5 $37.66   13.574%   $42.772   $42.77   $42.75   $42.80  
  Purchase #6 $239.52   10.651%   $265.0313   $265.03   $265.05   $265.00  
  Purchase #7 $202.77   4.320%   $211.5297   $211.53   $211.55   $211.50  
  7 purchase totals = $926.62       $1,014.2672   $1,014.26   $1,014.30   $1,014.20