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 $61.84   10.770%   $68.5002   $68.50   $68.50   $68.50  
  Purchase #2 $216.71   11.244%   $241.0769   $241.08   $241.10   $241.10  
  Purchase #3 $188.25   6.712%   $200.8853   $200.89   $200.90   $200.90  
  Purchase #4 $130.79   5.263%   $137.6735   $137.67   $137.65   $137.70  
  Purchase #5 $203.48   4.817%   $213.2816   $213.28   $213.30   $213.30  
  Purchase #6 $248.81   12.281%   $279.3664   $279.37   $279.35   $279.40  
  Purchase #7 $116.59   9.174%   $127.286   $127.29   $127.30   $127.30  
  7 purchase totals = $1,166.47       $1,268.0699   $1,268.08   $1,268.10   $1,268.20