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	$245.42	7.191%	$263.0682	$263.07	$263.05	$263.10
Purchase #2	$53.66	7.591%	$57.7333	$57.73	$57.75	$57.70
Purchase #3	$226.47	12.441%	$254.6451	$254.65	$254.65	$254.60
Purchase #4	$59.36	4.469%	$62.0128	$62.01	$62.00	$62.00
Purchase #5	$138.66	9.241%	$151.4736	$151.47	$151.45	$151.50
Purchase #6	$222.95	13.655%	$253.3938	$253.39	$253.40	$253.40
Purchase #7	$102.70	6.823%	$109.7072	$109.71	$109.70	$109.70
7 purchase totals =	$1,049.22		$1,152.0340	$1,152.03	$1,152.00	$1,152.00