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 $206.72   10.582%   $228.5951   $228.60   $228.60   $228.60  
  Purchase #2 $189.98   3.679%   $196.9694   $196.97   $196.95   $197.00  
  Purchase #3 $109.70   7.245%   $117.6478   $117.65   $117.65   $117.60  
  Purchase #4 $236.91   4.471%   $247.5022   $247.50   $247.50   $247.50  
  Purchase #5 $212.97   3.243%   $219.8766   $219.88   $219.90   $219.90  
  Purchase #6 $205.34   4.271%   $214.1101   $214.11   $214.10   $214.10  
  Purchase #7 $35.66   5.211%   $37.5182   $37.52   $37.50   $37.50  
  7 purchase totals = $1,197.28       $1,262.2194   $1,262.23   $1,262.20   $1,262.20