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 $59.78   3.212%   $61.7001   $61.70   $61.70   $61.70  
  Purchase #2 $33.88   11.816%   $37.8833   $37.88   $37.90   $37.90  
  Purchase #3 $212.78   8.721%   $231.3365   $231.34   $231.35   $231.30  
  Purchase #4 $160.43   11.380%   $178.6869   $178.69   $178.70   $178.70  
  Purchase #5 $111.50   5.409%   $117.531   $117.53   $117.55   $117.50  
  Purchase #6 $183.39   9.758%   $201.2852   $201.29   $201.30   $201.30  
  Purchase #7 $168.45   5.411%   $177.5648   $177.56   $177.55   $177.60  
  7 purchase totals = $930.21       $1,005.9878   $1,005.99   $1,006.05   $1,006.00