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 $193.99   4.421%   $202.5663   $202.57   $202.55   $202.60  
  Purchase #2 $97.35   13.335%   $110.3316   $110.33   $110.35   $110.30  
  Purchase #3 $135.70   6.549%   $144.587   $144.59   $144.60   $144.60  
  Purchase #4 $220.60   4.279%   $230.0395   $230.04   $230.05   $230.00  
  Purchase #5 $165.34   4.687%   $173.0895   $173.09   $173.10   $173.10  
  Purchase #6 $79.25   4.731%   $82.9993   $83.00   $83.00   $83.00  
  Purchase #7 $150.62   4.595%   $157.541   $157.54   $157.55   $157.50  
  7 purchase totals = $1,042.85       $1,101.1542   $1,101.16   $1,101.20   $1,101.10