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 $67.28   11.221%   $74.8295   $74.83   $74.85   $74.80  
  Purchase #2 $250.83   5.873%   $265.5612   $265.56   $265.55   $265.60  
  Purchase #3 $145.59   4.408%   $152.0076   $152.01   $152.00   $152.00  
  Purchase #4 $20.70   4.530%   $21.6377   $21.64   $21.65   $21.60  
  Purchase #5 $121.64   11.458%   $135.5775   $135.58   $135.60   $135.60  
  Purchase #6 $193.61   6.199%   $205.6119   $205.61   $205.60   $205.60  
  Purchase #7 $105.29   6.562%   $112.1991   $112.20   $112.20   $112.20  
  7 purchase totals = $904.94       $967.4245   $967.43   $967.45   $967.40