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 $69.95   7.214%   $74.9962   $75.00   $75.00   $75.00  
  Purchase #2 $117.28   13.368%   $132.958   $132.96   $132.95   $133.00  
  Purchase #3 $35.53   10.518%   $39.267   $39.27   $39.25   $39.30  
  Purchase #4 $232.53   11.764%   $259.8848   $259.88   $259.90   $259.90  
  Purchase #5 $235.40   6.489%   $250.6751   $250.68   $250.70   $250.70  
  Purchase #6 $239.49   11.110%   $266.0973   $266.10   $266.10   $266.10  
  Purchase #7 $123.44   6.853%   $131.8993   $131.90   $131.90   $131.90  
  7 purchase totals = $1,053.62       $1,155.7777   $1,155.79   $1,155.80   $1,155.90