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 $214.52   6.434%   $228.3222   $228.32   $228.30   $228.30  
  Purchase #2 $60.79   6.592%   $64.7973   $64.80   $64.80   $64.80  
  Purchase #3 $10.52   5.657%   $11.1151   $11.12   $11.10   $11.10  
  Purchase #4 $43.25   13.507%   $49.0918   $49.09   $49.10   $49.10  
  Purchase #5 $219.56   3.582%   $227.4246   $227.42   $227.40   $227.40  
  Purchase #6 $205.47   3.176%   $211.9957   $212.00   $212.00   $212.00  
  Purchase #7 $214.43   10.176%   $236.2504   $236.25   $236.25   $236.30  
  7 purchase totals = $968.54       $1,028.9971   $1,029.00   $1,028.95   $1,029.00