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 $68.74   7.287%   $73.7491   $73.75   $73.75   $73.70  
  Purchase #2 $127.39   5.482%   $134.3735   $134.37   $134.35   $134.40  
  Purchase #3 $225.49   11.297%   $250.9636   $250.96   $250.95   $251.00  
  Purchase #4 $8.89   5.873%   $9.4121   $9.41   $9.40   $9.40  
  Purchase #5 $202.94   8.419%   $220.0255   $220.03   $220.05   $220.00  
  Purchase #6 $133.39   6.384%   $141.9056   $141.91   $141.90   $141.90  
  Purchase #7 $202.58   13.735%   $230.4044   $230.40   $230.40   $230.40  
  7 purchase totals = $969.42       $1,060.8338   $1,060.83   $1,060.80   $1,060.80