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 $66.94   5.449%   $70.5876   $70.59   $70.60   $70.60  
  Purchase #2 $213.96   10.765%   $236.9928   $236.99   $237.00   $237.00  
  Purchase #3 $105.30   10.771%   $116.6419   $116.64   $116.65   $116.60  
  Purchase #4 $133.26   10.458%   $147.1963   $147.20   $147.20   $147.20  
  Purchase #5 $184.38   11.239%   $205.1025   $205.10   $205.10   $205.10  
  Purchase #6 $178.92   7.625%   $192.5627   $192.56   $192.55   $192.60  
  Purchase #7 $69.70   4.418%   $72.7793   $72.78   $72.80   $72.80  
  7 purchase totals = $952.46       $1,041.8631   $1,041.86   $1,041.90   $1,041.90