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 $212.80   13.344%   $241.196   $241.20   $241.20   $241.20  
  Purchase #2 $156.50   4.290%   $163.2139   $163.21   $163.20   $163.20  
  Purchase #3 $23.67   3.322%   $24.4563   $24.46   $24.45   $24.50  
  Purchase #4 $135.74   4.132%   $141.3488   $141.35   $141.35   $141.30  
  Purchase #5 $206.68   7.545%   $222.274   $222.27   $222.25   $222.30  
  Purchase #6 $173.75   10.570%   $192.1154   $192.12   $192.10   $192.10  
  Purchase #7 $16.30   6.375%   $17.3391   $17.34   $17.35   $17.30  
  7 purchase totals = $925.44       $1,001.9435   $1,001.95   $1,001.90   $1,001.90