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 $85.99   9.445%   $94.1118   $94.11   $94.10   $94.10  
  Purchase #2 $43.43   4.261%   $45.2806   $45.28   $45.30   $45.30  
  Purchase #3 $34.74   8.236%   $37.6012   $37.60   $37.60   $37.60  
  Purchase #4 $171.55   5.511%   $181.0041   $181.00   $181.00   $181.00  
  Purchase #5 $234.40   8.421%   $254.1388   $254.14   $254.15   $254.10  
  Purchase #6 $151.29   8.365%   $163.9454   $163.95   $163.95   $163.90  
  Purchase #7 $229.95   9.130%   $250.9444   $250.94   $250.95   $250.90  
  7 purchase totals = $951.35       $1,027.0263   $1,027.02   $1,027.05   $1,026.90