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	$58.72	6.213%	$62.3683	$62.37	$62.35	$62.40
Purchase #2	$185.79	13.212%	$210.3366	$210.34	$210.35	$210.30
Purchase #3	$209.93	4.250%	$218.852	$218.85	$218.85	$218.90
Purchase #4	$176.73	11.438%	$196.9444	$196.94	$196.95	$196.90
Purchase #5	$128.39	3.411%	$132.7694	$132.77	$132.75	$132.80
Purchase #6	$19.36	5.514%	$20.4275	$20.43	$20.45	$20.40
Purchase #7	$180.84	5.453%	$190.7012	$190.70	$190.70	$190.70
7 purchase totals =	$959.76		$1,032.3994	$1,032.40	$1,032.40	$1,032.40