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 $214.42   9.608%   $235.0215   $235.02   $235.00   $235.00  
  Purchase #2 $136.40   6.586%   $145.3833   $145.38   $145.40   $145.40  
  Purchase #3 $219.69   6.285%   $233.4975   $233.50   $233.50   $233.50  
  Purchase #4 $30.88   12.425%   $34.7168   $34.72   $34.70   $34.70  
  Purchase #5 $168.39   11.441%   $187.6555   $187.66   $187.65   $187.70  
  Purchase #6 $101.42   6.676%   $108.1908   $108.19   $108.20   $108.20  
  Purchase #7 $154.73   11.396%   $172.363   $172.36   $172.35   $172.40  
  7 purchase totals = $1,025.93       $1,116.8284   $1,116.83   $1,116.80   $1,116.90