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 $195.98   6.463%   $208.6462   $208.65   $208.65   $208.60  
  Purchase #2 $56.51   10.280%   $62.3192   $62.32   $62.30   $62.30  
  Purchase #3 $111.35   13.509%   $126.3923   $126.39   $126.40   $126.40  
  Purchase #4 $60.84   3.542%   $62.995   $63.00   $63.00   $63.00  
  Purchase #5 $243.78   3.106%   $251.3518   $251.35   $251.35   $251.40  
  Purchase #6 $193.51   13.227%   $219.1056   $219.11   $219.10   $219.10  
  Purchase #7 $151.87   13.643%   $172.5896   $172.59   $172.60   $172.60  
  7 purchase totals = $1,013.84       $1,103.3997   $1,103.41   $1,103.40   $1,103.40