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 $61.83   8.874%   $67.3168   $67.32   $67.30   $67.30  
  Purchase #2 $181.96   11.502%   $202.889   $202.89   $202.90   $202.90  
  Purchase #3 $213.51   3.288%   $220.5302   $220.53   $220.55   $220.50  
  Purchase #4 $230.75   13.812%   $262.6212   $262.62   $262.60   $262.60  
  Purchase #5 $80.45   6.413%   $85.6093   $85.61   $85.60   $85.60  
  Purchase #6 $6.93   6.562%   $7.3847   $7.38   $7.40   $7.40  
  Purchase #7 $200.54   10.547%   $221.691   $221.69   $221.70   $221.70  
  7 purchase totals = $975.97       $1,068.0422   $1,068.04   $1,068.05   $1,068.00