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	$232.79	12.545%	$261.9935	$261.99	$262.00	$262.00
Purchase #2	$196.29	11.459%	$218.7829	$218.78	$218.80	$218.80
Purchase #3	$237.80	4.354%	$248.1538	$248.15	$248.15	$248.20
Purchase #4	$130.30	7.749%	$140.3969	$140.40	$140.40	$140.40
Purchase #5	$124.90	3.187%	$128.8806	$128.88	$128.90	$128.90
Purchase #6	$54.39	10.423%	$60.0591	$60.06	$60.05	$60.10
Purchase #7	$38.96	9.348%	$42.602	$42.60	$42.60	$42.60
7 purchase totals =	$1,015.43		$1,100.8688	$1,100.86	$1,100.90	$1,101.00