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 $196.82   7.380%   $211.3453   $211.35   $211.35   $211.30  
  Purchase #2 $64.53   13.688%   $73.3629   $73.36   $73.35   $73.40  
  Purchase #3 $249.36   11.218%   $277.3332   $277.33   $277.35   $277.30  
  Purchase #4 $244.43   7.372%   $262.4494   $262.45   $262.45   $262.40  
  Purchase #5 $7.88   8.653%   $8.5619   $8.56   $8.55   $8.60  
  Purchase #6 $202.95   6.745%   $216.639   $216.64   $216.65   $216.60  
  Purchase #7 $50.39   3.331%   $52.0685   $52.07   $52.05   $52.10  
  7 purchase totals = $1,016.36       $1,101.7602   $1,101.76   $1,101.75   $1,101.70