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 $32.54   10.566%   $35.9782   $35.98   $36.00   $36.00  
  Purchase #2 $179.68   11.633%   $200.5822   $200.58   $200.60   $200.60  
  Purchase #3 $172.62   10.820%   $191.2975   $191.30   $191.30   $191.30  
  Purchase #4 $242.42   4.337%   $252.9338   $252.93   $252.95   $252.90  
  Purchase #5 $65.55   5.558%   $69.1933   $69.19   $69.20   $69.20  
  Purchase #6 $97.60   4.343%   $101.8388   $101.84   $101.85   $101.80  
  Purchase #7 $219.99   10.642%   $243.4013   $243.40   $243.40   $243.40  
  7 purchase totals = $1,010.40       $1,095.2251   $1,095.22   $1,095.30   $1,095.20