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 $183.93   8.745%   $200.0147   $200.01   $200.00   $200.00  
  Purchase #2 $126.54   9.139%   $138.1045   $138.10   $138.10   $138.10  
  Purchase #3 $22.87   3.364%   $23.6393   $23.64   $23.65   $23.60  
  Purchase #4 $150.34   3.726%   $155.9417   $155.94   $155.95   $155.90  
  Purchase #5 $175.26   11.721%   $195.8022   $195.80   $195.80   $195.80  
  Purchase #6 $150.32   3.330%   $155.3257   $155.33   $155.35   $155.30  
  Purchase #7 $160.91   7.255%   $172.584   $172.58   $172.60   $172.60  
  7 purchase totals = $970.17       $1,041.4121   $1,041.40   $1,041.45   $1,041.30