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 $94.77   3.619%   $98.1997   $98.20   $98.20   $98.20  
  Purchase #2 $244.88   3.527%   $253.5169   $253.52   $253.50   $253.50  
  Purchase #3 $132.25   11.639%   $147.6426   $147.64   $147.65   $147.60  
  Purchase #4 $133.45   9.134%   $145.6393   $145.64   $145.65   $145.60  
  Purchase #5 $177.83   6.470%   $189.3356   $189.34   $189.35   $189.30  
  Purchase #6 $208.27   5.508%   $219.7415   $219.74   $219.75   $219.70  
  Purchase #7 $48.50   9.259%   $52.9906   $52.99   $53.00   $53.00  
  7 purchase totals = $1,039.95       $1,107.0662   $1,107.07   $1,107.10   $1,106.90