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 $224.93   7.568%   $241.9527   $241.95   $241.95   $242.00  
  Purchase #2 $154.58   6.595%   $164.7746   $164.77   $164.75   $164.80  
  Purchase #3 $220.49   12.411%   $247.855   $247.86   $247.85   $247.90  
  Purchase #4 $202.60   5.664%   $214.0753   $214.08   $214.10   $214.10  
  Purchase #5 $60.74   7.858%   $65.5129   $65.51   $65.50   $65.50  
  Purchase #6 $131.90   13.236%   $149.3583   $149.36   $149.35   $149.40  
  Purchase #7 $196.97   7.621%   $211.9811   $211.98   $212.00   $212.00  
  7 purchase totals = $1,192.21       $1,295.5099   $1,295.51   $1,295.50   $1,295.70