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	$200.58	4.559%	$209.7244	$209.72	$209.70	$209.70
Purchase #2	$142.44	9.796%	$156.3934	$156.39	$156.40	$156.40
Purchase #3	$204.54	9.246%	$223.4518	$223.45	$223.45	$223.50
Purchase #4	$53.63	3.640%	$55.5821	$55.58	$55.60	$55.60
Purchase #5	$42.77	10.249%	$47.1535	$47.15	$47.15	$47.20
Purchase #6	$231.83	13.760%	$263.7298	$263.73	$263.75	$263.70
Purchase #7	$178.25	3.173%	$183.9059	$183.91	$183.90	$183.90
7 purchase totals =	$1,054.04		$1,139.9409	$1,139.93	$1,139.95	$1,140.00