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 $181.51   7.753%   $195.5825   $195.58   $195.60   $195.60  
  Purchase #2 $41.39   11.608%   $46.1946   $46.19   $46.20   $46.20  
  Purchase #3 $27.65   9.252%   $30.2082   $30.21   $30.20   $30.20  
  Purchase #4 $98.48   8.817%   $107.163   $107.16   $107.15   $107.20  
  Purchase #5 $156.78   5.593%   $165.5487   $165.55   $165.55   $165.50  
  Purchase #6 $50.64   12.245%   $56.8409   $56.84   $56.85   $56.80  
  Purchase #7 $239.58   3.102%   $247.0118   $247.01   $247.00   $247.00  
  7 purchase totals = $796.03       $848.5497   $848.54   $848.55   $848.50