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 $62.50   11.252%   $69.5325   $69.53   $69.55   $69.50  
  Purchase #2 $72.92   5.615%   $77.0145   $77.01   $77.00   $77.00  
  Purchase #3 $177.67   8.263%   $192.3509   $192.35   $192.35   $192.40  
  Purchase #4 $203.57   6.656%   $217.1196   $217.12   $217.10   $217.10  
  Purchase #5 $209.47   4.801%   $219.5267   $219.53   $219.55   $219.50  
  Purchase #6 $73.77   6.286%   $78.4072   $78.41   $78.40   $78.40  
  Purchase #7 $59.64   7.538%   $64.1357   $64.14   $64.15   $64.10  
  7 purchase totals = $859.54       $918.0871   $918.09   $918.10   $918.00