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 $201.46   6.482%   $214.5186   $214.52   $214.50   $214.50  
  Purchase #2 $222.65   4.647%   $232.9965   $233.00   $233.00   $233.00  
  Purchase #3 $156.34   10.502%   $172.7588   $172.76   $172.75   $172.80  
  Purchase #4 $207.91   5.569%   $219.4885   $219.49   $219.50   $219.50  
  Purchase #5 $55.90   13.469%   $63.4292   $63.43   $63.45   $63.40  
  Purchase #6 $191.70   10.620%   $212.0585   $212.06   $212.05   $212.10  
  Purchase #7 $19.93   13.603%   $22.6411   $22.64   $22.65   $22.60  
  7 purchase totals = $1,055.89       $1,137.8912   $1,137.90   $1,137.90   $1,137.90