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	$221.32	9.704%	$242.7969	$242.80	$242.80	$242.80
Purchase #2	$190.61	8.762%	$207.3112	$207.31	$207.30	$207.30
Purchase #3	$47.70	13.426%	$54.1042	$54.10	$54.10	$54.10
Purchase #4	$170.26	3.453%	$176.1391	$176.14	$176.15	$176.10
Purchase #5	$38.27	4.153%	$39.8594	$39.86	$39.85	$39.90
Purchase #6	$83.55	7.380%	$89.716	$89.72	$89.70	$89.70
Purchase #7	$229.32	4.849%	$240.4397	$240.44	$240.45	$240.40
7 purchase totals =	$981.03		$1,050.3665	$1,050.37	$1,050.35	$1,050.30