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	$8.97	12.195%	$10.0639	$10.06	$10.05	$10.10
Purchase #2	$11.74	11.808%	$13.1263	$13.13	$13.15	$13.10
Purchase #3	$65.91	6.383%	$70.117	$70.12	$70.10	$70.10
Purchase #4	$119.35	7.469%	$128.2643	$128.26	$128.25	$128.30
Purchase #5	$40.98	3.150%	$42.2709	$42.27	$42.25	$42.30
Purchase #6	$98.91	13.130%	$111.8969	$111.90	$111.90	$111.90
Purchase #7	$163.45	4.871%	$171.4116	$171.41	$171.40	$171.40
7 purchase totals =	$509.31		$547.1509	$547.15	$547.10	$547.20