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 $68.93   6.807%   $73.6221   $73.62   $73.60   $73.60  
  Purchase #2 $183.51   11.619%   $204.832   $204.83   $204.85   $204.80  
  Purchase #3 $191.78   7.793%   $206.7254   $206.73   $206.75   $206.70  
  Purchase #4 $179.54   10.745%   $198.8316   $198.83   $198.85   $198.80  
  Purchase #5 $161.37   11.565%   $180.0324   $180.03   $180.05   $180.00  
  Purchase #6 $219.99   8.397%   $238.4626   $238.46   $238.45   $238.50  
  Purchase #7 $195.93   3.139%   $202.0802   $202.08   $202.10   $202.10  
  7 purchase totals = $1,201.05       $1,304.5863   $1,304.58   $1,304.65   $1,304.50