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 $173.50   12.794%   $195.6976   $195.70   $195.70   $195.70  
  Purchase #2 $228.89   9.383%   $250.3667   $250.37   $250.35   $250.40  
  Purchase #3 $21.59   11.724%   $24.1212   $24.12   $24.10   $24.10  
  Purchase #4 $229.56   6.667%   $244.8648   $244.86   $244.85   $244.90  
  Purchase #5 $95.46   3.585%   $98.8822   $98.88   $98.90   $98.90  
  Purchase #6 $172.83   12.518%   $194.4649   $194.46   $194.45   $194.50  
  Purchase #7 $122.43   5.475%   $129.133   $129.13   $129.15   $129.10  
  7 purchase totals = $1,044.26       $1,137.5304   $1,137.52   $1,137.50   $1,137.60