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 $69.37   6.683%   $74.006   $74.01   $74.00   $74.00  
  Purchase #2 $67.46   7.235%   $72.3407   $72.34   $72.35   $72.30  
  Purchase #3 $204.57   8.452%   $221.8603   $221.86   $221.85   $221.90  
  Purchase #4 $188.96   11.436%   $210.5695   $210.57   $210.55   $210.60  
  Purchase #5 $115.90   7.521%   $124.6168   $124.62   $124.60   $124.60  
  Purchase #6 $167.76   6.324%   $178.3691   $178.37   $178.35   $178.40  
  Purchase #7 $187.41   7.720%   $201.8781   $201.88   $201.90   $201.90  
  7 purchase totals = $1,001.43       $1,083.6405   $1,083.65   $1,083.60   $1,083.70