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	$226.88	3.816%	$235.5377	$235.54	$235.55	$235.50
Purchase #2	$247.99	12.159%	$278.1431	$278.14	$278.15	$278.10
Purchase #3	$116.46	10.417%	$128.5916	$128.59	$128.60	$128.60
Purchase #4	$10.69	7.280%	$11.4682	$11.47	$11.45	$11.50
Purchase #5	$39.48	9.723%	$43.3186	$43.32	$43.30	$43.30
Purchase #6	$221.35	6.371%	$235.4522	$235.45	$235.45	$235.50
Purchase #7	$145.96	4.564%	$152.6216	$152.62	$152.60	$152.60
7 purchase totals =	$1,008.81		$1,085.1330	$1,085.13	$1,085.10	$1,085.10