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 $44.42   5.692%   $46.9484   $46.95   $46.95   $46.90  
  Purchase #2 $24.32   12.266%   $27.3031   $27.30   $27.30   $27.30  
  Purchase #3 $16.88   6.700%   $18.011   $18.01   $18.00   $18.00  
  Purchase #4 $149.84   10.332%   $165.3215   $165.32   $165.30   $165.30  
  Purchase #5 $233.46   8.215%   $252.6387   $252.64   $252.65   $252.60  
  Purchase #6 $197.80   5.592%   $208.861   $208.86   $208.85   $208.90  
  Purchase #7 $210.45   4.332%   $219.5667   $219.57   $219.55   $219.60  
  7 purchase totals = $877.17       $938.6504   $938.65   $938.60   $938.60