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 $58.86   13.843%   $67.008   $67.01   $67.00   $67.00  
  Purchase #2 $201.97   9.860%   $221.8842   $221.88   $221.90   $221.90  
  Purchase #3 $39.82   4.740%   $41.7075   $41.71   $41.70   $41.70  
  Purchase #4 $248.46   7.790%   $267.815   $267.82   $267.80   $267.80  
  Purchase #5 $153.71   12.671%   $173.1866   $173.19   $173.20   $173.20  
  Purchase #6 $98.64   13.127%   $111.5885   $111.59   $111.60   $111.60  
  Purchase #7 $205.84   4.350%   $214.794   $214.79   $214.80   $214.80  
  7 purchase totals = $1,007.30       $1,097.9838   $1,097.99   $1,098.00   $1,098.00