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	$210.53	5.768%	$222.6734	$222.67	$222.65	$222.70
Purchase #2	$71.52	10.826%	$79.2628	$79.26	$79.25	$79.30
Purchase #3	$37.76	11.140%	$41.9665	$41.97	$41.95	$42.00
Purchase #4	$182.52	12.778%	$205.8424	$205.84	$205.85	$205.80
Purchase #5	$118.85	11.497%	$132.5142	$132.51	$132.50	$132.50
Purchase #6	$88.55	3.640%	$91.7732	$91.77	$91.75	$91.80
Purchase #7	$134.45	10.291%	$148.2862	$148.29	$148.30	$148.30
7 purchase totals =	$844.18		$922.3187	$922.31	$922.25	$922.40