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 $162.60   5.163%   $170.995   $171.00   $171.00   $171.00  
  Purchase #2 $173.36   12.290%   $194.6659   $194.67   $194.65   $194.70  
  Purchase #3 $192.34   8.165%   $208.0446   $208.04   $208.05   $208.00  
  Purchase #4 $173.65   10.659%   $192.1594   $192.16   $192.15   $192.20  
  Purchase #5 $163.55   5.721%   $172.9067   $172.91   $172.90   $172.90  
  Purchase #6 $228.25   10.185%   $251.4973   $251.50   $251.50   $251.50  
  Purchase #7 $14.44   10.781%   $15.9968   $16.00   $16.00   $16.00  
  7 purchase totals = $1,108.19       $1,206.2657   $1,206.28   $1,206.25   $1,206.30