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 $175.41   11.181%   $195.0226   $195.02   $195.00   $195.00  
  Purchase #2 $54.69   12.148%   $61.3337   $61.33   $61.35   $61.30  
  Purchase #3 $146.74   3.526%   $151.9141   $151.91   $151.90   $151.90  
  Purchase #4 $143.35   7.294%   $153.8059   $153.81   $153.80   $153.80  
  Purchase #5 $40.57   8.706%   $44.102   $44.10   $44.10   $44.10  
  Purchase #6 $199.51   3.416%   $206.3253   $206.33   $206.35   $206.30  
  Purchase #7 $200.80   3.540%   $207.9083   $207.91   $207.90   $207.90  
  7 purchase totals = $961.07       $1,020.4119   $1,020.41   $1,020.40   $1,020.30