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 $117.86   7.381%   $126.5592   $126.56   $126.55   $126.60  
  Purchase #2 $156.39   6.828%   $167.0683   $167.07   $167.05   $167.10  
  Purchase #3 $189.97   12.558%   $213.8264   $213.83   $213.85   $213.80  
  Purchase #4 $95.75   10.478%   $105.7827   $105.78   $105.80   $105.80  
  Purchase #5 $13.77   4.654%   $14.4109   $14.41   $14.40   $14.40  
  Purchase #6 $178.66   9.398%   $195.4505   $195.45   $195.45   $195.50  
  Purchase #7 $243.55   10.163%   $268.302   $268.30   $268.30   $268.30  
  7 purchase totals = $995.95       $1,091.4000   $1,091.40   $1,091.40   $1,091.50