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 $72.59   5.521%   $76.5977   $76.60   $76.60   $76.60  
  Purchase #2 $88.50   13.194%   $100.1767   $100.18   $100.20   $100.20  
  Purchase #3 $112.88   5.332%   $118.8988   $118.90   $118.90   $118.90  
  Purchase #4 $137.88   3.685%   $142.9609   $142.96   $142.95   $143.00  
  Purchase #5 $156.96   10.611%   $173.615   $173.62   $173.60   $173.60  
  Purchase #6 $203.50   11.529%   $226.9615   $226.96   $226.95   $227.00  
  Purchase #7 $195.92   11.843%   $219.1228   $219.12   $219.10   $219.10  
  7 purchase totals = $968.23       $1,058.3334   $1,058.34   $1,058.30   $1,058.40