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 $92.80   3.486%   $96.035   $96.04   $96.05   $96.00  
  Purchase #2 $191.89   6.500%   $204.3629   $204.36   $204.35   $204.40  
  Purchase #3 $204.47   4.673%   $214.0249   $214.02   $214.00   $214.00  
  Purchase #4 $215.46   10.109%   $237.2409   $237.24   $237.25   $237.20  
  Purchase #5 $235.32   4.854%   $246.7424   $246.74   $246.75   $246.70  
  Purchase #6 $62.59   11.822%   $69.9894   $69.99   $70.00   $70.00  
  Purchase #7 $212.55   7.328%   $228.1257   $228.13   $228.15   $228.10  
  7 purchase totals = $1,215.08       $1,296.5212   $1,296.52   $1,296.55   $1,296.40