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	$91.85	13.851%	$104.5721	$104.57	$104.55	$104.60
Purchase #2	$121.86	7.708%	$131.253	$131.25	$131.25	$131.30
Purchase #3	$40.67	7.869%	$43.8703	$43.87	$43.85	$43.90
Purchase #4	$6.42	13.583%	$7.292	$7.29	$7.30	$7.30
Purchase #5	$19.94	10.604%	$22.0544	$22.05	$22.05	$22.10
Purchase #6	$52.86	5.283%	$55.6526	$55.65	$55.65	$55.70
Purchase #7	$92.66	5.344%	$97.6118	$97.61	$97.60	$97.60
7 purchase totals =	$426.26		$462.3062	$462.29	$462.25	$462.50