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 $92.89   5.809%   $98.286   $98.29   $98.30   $98.30  
  Purchase #2 $149.91   7.480%   $161.1233   $161.12   $161.10   $161.10  
  Purchase #3 $59.46   8.706%   $64.6366   $64.64   $64.65   $64.60  
  Purchase #4 $197.25   8.191%   $213.4067   $213.41   $213.40   $213.40  
  Purchase #5 $27.64   10.720%   $30.603   $30.60   $30.60   $30.60  
  Purchase #6 $238.33   7.640%   $256.5384   $256.54   $256.55   $256.50  
  Purchase #7 $210.78   5.650%   $222.6891   $222.69   $222.70   $222.70  
  7 purchase totals = $976.26       $1,047.2831   $1,047.29   $1,047.30   $1,047.20