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 $170.39   3.266%   $175.9549   $175.95   $175.95   $176.00  
  Purchase #2 $83.99   9.223%   $91.7364   $91.74   $91.75   $91.70  
  Purchase #3 $144.56   4.394%   $150.912   $150.91   $150.90   $150.90  
  Purchase #4 $248.78   5.543%   $262.5699   $262.57   $262.55   $262.60  
  Purchase #5 $117.53   10.203%   $129.5216   $129.52   $129.50   $129.50  
  Purchase #6 $161.69   7.298%   $173.4901   $173.49   $173.50   $173.50  
  Purchase #7 $215.35   3.735%   $223.3933   $223.39   $223.40   $223.40  
  7 purchase totals = $1,142.29       $1,207.5782   $1,207.57   $1,207.55   $1,207.60