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 $64.35   11.819%   $71.9555   $71.96   $71.95   $72.00  
  Purchase #2 $246.34   12.729%   $277.6966   $277.70   $277.70   $277.70  
  Purchase #3 $210.27   10.714%   $232.7983   $232.80   $232.80   $232.80  
  Purchase #4 $190.44   3.842%   $197.7567   $197.76   $197.75   $197.80  
  Purchase #5 $208.67   4.810%   $218.707   $218.71   $218.70   $218.70  
  Purchase #6 $105.28   11.686%   $117.583   $117.58   $117.60   $117.60  
  Purchase #7 $74.85   7.419%   $80.4031   $80.40   $80.40   $80.40  
  7 purchase totals = $1,100.20       $1,196.9002   $1,196.91   $1,196.90   $1,197.00