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 $41.84   13.764%   $47.5989   $47.60   $47.60   $47.60  
  Purchase #2 $13.51   5.158%   $14.2068   $14.21   $14.20   $14.20  
  Purchase #3 $212.69   9.451%   $232.7913   $232.79   $232.80   $232.80  
  Purchase #4 $20.31   8.160%   $21.9673   $21.97   $21.95   $22.00  
  Purchase #5 $37.99   13.625%   $43.1661   $43.17   $43.15   $43.20  
  Purchase #6 $152.57   10.334%   $168.3366   $168.34   $168.35   $168.30  
  Purchase #7 $219.25   12.169%   $245.9305   $245.93   $245.95   $245.90  
  7 purchase totals = $698.16       $773.9975   $774.01   $774.00   $774.00