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 $213.99   8.409%   $231.9844   $231.98   $232.00   $232.00  
  Purchase #2 $32.55   5.542%   $34.3539   $34.35   $34.35   $34.40  
  Purchase #3 $68.64   4.364%   $71.6354   $71.64   $71.65   $71.60  
  Purchase #4 $148.43   4.697%   $155.4018   $155.40   $155.40   $155.40  
  Purchase #5 $32.81   11.118%   $36.4578   $36.46   $36.45   $36.50  
  Purchase #6 $153.56   7.712%   $165.4025   $165.40   $165.40   $165.40  
  Purchase #7 $215.66   9.411%   $235.9558   $235.96   $235.95   $236.00  
  7 purchase totals = $865.64       $931.1916   $931.19   $931.20   $931.30