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 $238.46   10.337%   $263.1096   $263.11   $263.10   $263.10  
  Purchase #2 $201.52   3.133%   $207.8336   $207.83   $207.85   $207.80  
  Purchase #3 $60.84   9.430%   $66.5772   $66.58   $66.60   $66.60  
  Purchase #4 $196.87   10.757%   $218.0473   $218.05   $218.05   $218.00  
  Purchase #5 $12.57   6.228%   $13.3529   $13.35   $13.35   $13.40  
  Purchase #6 $33.91   3.829%   $35.2084   $35.21   $35.20   $35.20  
  Purchase #7 $192.26   10.202%   $211.8744   $211.87   $211.85   $211.90  
  7 purchase totals = $936.43       $1,016.0034   $1,016.00   $1,016.00   $1,016.00