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 $216.42   13.185%   $244.955   $244.96   $244.95   $245.00  
  Purchase #2 $75.71   4.826%   $79.3638   $79.36   $79.35   $79.40  
  Purchase #3 $93.96   6.662%   $100.2196   $100.22   $100.20   $100.20  
  Purchase #4 $176.69   9.335%   $193.184   $193.18   $193.20   $193.20  
  Purchase #5 $237.35   3.852%   $246.4927   $246.49   $246.50   $246.50  
  Purchase #6 $228.81   8.163%   $247.4878   $247.49   $247.50   $247.50  
  Purchase #7 $71.47   12.373%   $80.313   $80.31   $80.30   $80.30  
  7 purchase totals = $1,100.41       $1,192.0159   $1,192.01   $1,192.00   $1,192.10