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 $34.81   6.169%   $36.9574   $36.96   $36.95   $37.00  
  Purchase #2 $212.67   9.561%   $233.0034   $233.00   $233.00   $233.00  
  Purchase #3 $203.26   10.734%   $225.0779   $225.08   $225.10   $225.10  
  Purchase #4 $169.46   3.476%   $175.3504   $175.35   $175.35   $175.40  
  Purchase #5 $108.84   4.807%   $114.0719   $114.07   $114.05   $114.10  
  Purchase #6 $236.39   13.741%   $268.8723   $268.87   $268.85   $268.90  
  Purchase #7 $116.27   12.116%   $130.3573   $130.36   $130.35   $130.40  
  7 purchase totals = $1,081.70       $1,183.6906   $1,183.69   $1,183.65   $1,183.90