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 $198.69   13.872%   $226.2523   $226.25   $226.25   $226.30  
  Purchase #2 $152.86   13.817%   $173.9807   $173.98   $174.00   $174.00  
  Purchase #3 $88.96   8.285%   $96.3303   $96.33   $96.35   $96.30  
  Purchase #4 $207.57   3.214%   $214.2413   $214.24   $214.25   $214.20  
  Purchase #5 $205.91   13.851%   $234.4306   $234.43   $234.45   $234.40  
  Purchase #6 $191.47   3.635%   $198.4299   $198.43   $198.45   $198.40  
  Purchase #7 $62.39   11.633%   $69.6478   $69.65   $69.65   $69.60  
  7 purchase totals = $1,107.85       $1,213.3129   $1,213.31   $1,213.40   $1,213.20