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 $34.76   3.485%   $35.9714   $35.97   $35.95   $36.00  
  Purchase #2 $168.83   4.139%   $175.8179   $175.82   $175.80   $175.80  
  Purchase #3 $34.54   8.166%   $37.3605   $37.36   $37.35   $37.40  
  Purchase #4 $26.93   10.168%   $29.6682   $29.67   $29.65   $29.70  
  Purchase #5 $101.40   6.182%   $107.6685   $107.67   $107.65   $107.70  
  Purchase #6 $135.91   5.205%   $142.9841   $142.98   $143.00   $143.00  
  Purchase #7 $228.26   3.867%   $237.0868   $237.09   $237.10   $237.10  
  7 purchase totals = $730.63       $766.5574   $766.56   $766.50   $766.70