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 $37.52   10.719%   $41.5418   $41.54   $41.55   $41.50  
  Purchase #2 $164.81   6.634%   $175.7435   $175.74   $175.75   $175.70  
  Purchase #3 $138.59   4.705%   $145.1107   $145.11   $145.10   $145.10  
  Purchase #4 $168.57   8.488%   $182.8782   $182.88   $182.90   $182.90  
  Purchase #5 $127.96   13.629%   $145.3997   $145.40   $145.40   $145.40  
  Purchase #6 $111.29   4.342%   $116.1222   $116.12   $116.10   $116.10  
  Purchase #7 $177.62   11.336%   $197.755   $197.76   $197.75   $197.80  
  7 purchase totals = $926.36       $1,004.5511   $1,004.55   $1,004.55   $1,004.50