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 $71.99   3.436%   $74.4636   $74.46   $74.45   $74.50  
  Purchase #2 $128.73   4.705%   $134.7867   $134.79   $134.80   $134.80  
  Purchase #3 $111.67   6.825%   $119.2915   $119.29   $119.30   $119.30  
  Purchase #4 $149.57   10.615%   $165.4469   $165.45   $165.45   $165.40  
  Purchase #5 $125.35   3.336%   $129.5317   $129.53   $129.55   $129.50  
  Purchase #6 $239.69   5.727%   $253.417   $253.42   $253.40   $253.40  
  Purchase #7 $178.51   3.605%   $184.9453   $184.95   $184.95   $184.90  
  7 purchase totals = $1,005.51       $1,061.8827   $1,061.89   $1,061.90   $1,061.80