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 $213.29   11.595%   $238.021   $238.02   $238.00   $238.00  
  Purchase #2 $62.26   7.229%   $66.7608   $66.76   $66.75   $66.80  
  Purchase #3 $89.65   11.140%   $99.637   $99.64   $99.65   $99.60  
  Purchase #4 $201.77   9.203%   $220.3389   $220.34   $220.35   $220.30  
  Purchase #5 $202.81   8.680%   $220.4139   $220.41   $220.40   $220.40  
  Purchase #6 $74.94   8.742%   $81.4913   $81.49   $81.50   $81.50  
  Purchase #7 $175.27   3.485%   $181.3782   $181.38   $181.40   $181.40  
  7 purchase totals = $1,019.99       $1,108.0411   $1,108.04   $1,108.05   $1,108.00