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 $214.85   9.383%   $235.0094   $235.01   $235.00   $235.00  
  Purchase #2 $5.79   5.569%   $6.1124   $6.11   $6.10   $6.10  
  Purchase #3 $63.36   5.500%   $66.8448   $66.84   $66.85   $66.80  
  Purchase #4 $173.74   4.204%   $181.044   $181.04   $181.05   $181.00  
  Purchase #5 $241.95   4.830%   $253.6362   $253.64   $253.65   $253.60  
  Purchase #6 $217.74   13.153%   $246.3793   $246.38   $246.40   $246.40  
  Purchase #7 $46.68   13.686%   $53.0686   $53.07   $53.05   $53.10  
  7 purchase totals = $964.11       $1,042.0947   $1,042.09   $1,042.10   $1,042.00