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	$224.85	3.671%	$233.1042	$233.10	$233.10	$233.10
Purchase #2	$31.43	12.473%	$35.3503	$35.35	$35.35	$35.40
Purchase #3	$112.90	8.851%	$122.8928	$122.89	$122.90	$122.90
Purchase #4	$148.82	9.285%	$162.6379	$162.64	$162.65	$162.60
Purchase #5	$154.45	10.304%	$170.3645	$170.36	$170.35	$170.40
Purchase #6	$221.32	11.858%	$247.5641	$247.56	$247.55	$247.60
Purchase #7	$205.82	4.754%	$215.6047	$215.60	$215.60	$215.60
7 purchase totals =	$1,099.59		$1,187.5185	$1,187.50	$1,187.50	$1,187.60