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	$194.58	10.615%	$215.2347	$215.23	$215.25	$215.20
Purchase #2	$98.74	12.719%	$111.2987	$111.30	$111.30	$111.30
Purchase #3	$82.66	8.142%	$89.3902	$89.39	$89.40	$89.40
Purchase #4	$32.58	9.106%	$35.5467	$35.55	$35.55	$35.50
Purchase #5	$100.42	4.619%	$105.0584	$105.06	$105.05	$105.10
Purchase #6	$95.68	5.193%	$100.6487	$100.65	$100.65	$100.60
Purchase #7	$198.88	11.411%	$221.5742	$221.57	$221.55	$221.60
7 purchase totals =	$803.54		$878.7516	$878.75	$878.75	$878.70