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 $218.67   11.582%   $243.9964   $244.00   $244.00   $244.00  
  Purchase #2 $150.54   3.157%   $155.2925   $155.29   $155.30   $155.30  
  Purchase #3 $167.46   3.438%   $173.2173   $173.22   $173.20   $173.20  
  Purchase #4 $111.82   12.290%   $125.5627   $125.56   $125.55   $125.60  
  Purchase #5 $23.49   11.509%   $26.1935   $26.19   $26.20   $26.20  
  Purchase #6 $163.45   9.772%   $179.4223   $179.42   $179.40   $179.40  
  Purchase #7 $201.71   9.165%   $220.1967   $220.20   $220.20   $220.20  
  7 purchase totals = $1,037.14       $1,123.8814   $1,123.88   $1,123.85   $1,123.90