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	$224.86	9.471%	$246.1565	$246.16	$246.15	$246.20
Purchase #2	$158.61	12.462%	$178.376	$178.38	$178.40	$178.40
Purchase #3	$86.36	3.490%	$89.374	$89.37	$89.35	$89.40
Purchase #4	$229.78	12.393%	$258.2566	$258.26	$258.25	$258.30
Purchase #5	$82.46	8.488%	$89.4592	$89.46	$89.45	$89.50
Purchase #6	$203.92	3.351%	$210.7534	$210.75	$210.75	$210.80
Purchase #7	$145.66	9.463%	$159.4438	$159.44	$159.45	$159.40
7 purchase totals =	$1,131.65		$1,231.8195	$1,231.82	$1,231.80	$1,232.00