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 $184.76   4.167%   $192.4589   $192.46   $192.45   $192.50  
  Purchase #2 $36.41   13.193%   $41.2136   $41.21   $41.20   $41.20  
  Purchase #3 $45.75   11.861%   $51.1764   $51.18   $51.20   $51.20  
  Purchase #4 $181.69   12.365%   $204.156   $204.16   $204.15   $204.20  
  Purchase #5 $117.50   3.618%   $121.7512   $121.75   $121.75   $121.80  
  Purchase #6 $198.85   8.519%   $215.79   $215.79   $215.80   $215.80  
  Purchase #7 $190.76   7.833%   $205.7022   $205.70   $205.70   $205.70  
  7 purchase totals = $955.72       $1,032.2483   $1,032.25   $1,032.25   $1,032.40