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 $183.97   6.366%   $195.6815   $195.68   $195.70   $195.70  
  Purchase #2 $224.56   10.338%   $247.775   $247.78   $247.80   $247.80  
  Purchase #3 $189.69   13.187%   $214.7044   $214.70   $214.70   $214.70  
  Purchase #4 $114.25   4.720%   $119.6426   $119.64   $119.65   $119.60  
  Purchase #5 $249.43   4.568%   $260.824   $260.82   $260.80   $260.80  
  Purchase #6 $152.75   8.305%   $165.4359   $165.44   $165.45   $165.40  
  Purchase #7 $142.52   5.765%   $150.7363   $150.74   $150.75   $150.70  
  7 purchase totals = $1,257.17       $1,354.7997   $1,354.80   $1,354.85   $1,354.70