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 $43.86   9.531%   $48.0403   $48.04   $48.05   $48.00  
  Purchase #2 $115.87   3.377%   $119.7829   $119.78   $119.80   $119.80  
  Purchase #3 $21.91   9.711%   $24.0377   $24.04   $24.05   $24.00  
  Purchase #4 $198.64   13.861%   $226.1735   $226.17   $226.15   $226.20  
  Purchase #5 $70.51   8.438%   $76.4596   $76.46   $76.45   $76.50  
  Purchase #6 $210.45   10.416%   $232.3705   $232.37   $232.35   $232.40  
  Purchase #7 $205.70   7.545%   $221.2201   $221.22   $221.20   $221.20  
  7 purchase totals = $866.94       $948.0846   $948.08   $948.05   $948.10