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	$224.30	6.519%	$238.9221	$238.92	$238.90	$238.90
Purchase #2	$238.37	3.508%	$246.732	$246.73	$246.75	$246.70
Purchase #3	$107.81	3.384%	$111.4583	$111.46	$111.45	$111.50
Purchase #4	$105.75	13.757%	$120.298	$120.30	$120.30	$120.30
Purchase #5	$36.60	9.868%	$40.2117	$40.21	$40.20	$40.20
Purchase #6	$79.87	11.602%	$89.1365	$89.14	$89.15	$89.10
Purchase #7	$199.78	13.842%	$227.4335	$227.43	$227.45	$227.40
7 purchase totals =	$992.48		$1,074.1921	$1,074.19	$1,074.20	$1,074.10