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	$100.61	11.636%	$112.317	$112.32	$112.30	$112.30
Purchase #2	$81.61	10.644%	$90.2966	$90.30	$90.30	$90.30
Purchase #3	$50.98	9.838%	$55.9954	$56.00	$56.00	$56.00
Purchase #4	$131.27	13.415%	$148.8799	$148.88	$148.90	$148.90
Purchase #5	$57.36	11.718%	$64.0814	$64.08	$64.10	$64.10
Purchase #6	$9.40	3.815%	$9.7586	$9.76	$9.75	$9.80
Purchase #7	$208.46	12.131%	$233.7483	$233.75	$233.75	$233.70
7 purchase totals =	$639.69		$715.0772	$715.09	$715.10	$715.10