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 $66.35   5.363%   $69.9084   $69.91   $69.90   $69.90  
  Purchase #2 $191.89   3.582%   $198.7635   $198.76   $198.75   $198.80  
  Purchase #3 $197.56   11.195%   $219.6768   $219.68   $219.70   $219.70  
  Purchase #4 $142.41   3.749%   $147.749   $147.75   $147.75   $147.70  
  Purchase #5 $221.33   10.289%   $244.1026   $244.10   $244.10   $244.10  
  Purchase #6 $87.32   7.393%   $93.7756   $93.78   $93.80   $93.80  
  Purchase #7 $38.48   4.702%   $40.2893   $40.29   $40.30   $40.30  
  7 purchase totals = $945.34       $1,014.2652   $1,014.27   $1,014.30   $1,014.30