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	$75.71	5.439%	$79.8279	$79.83	$79.85	$79.80
Purchase #2	$86.30	4.668%	$90.3285	$90.33	$90.35	$90.30
Purchase #3	$52.94	9.684%	$58.0667	$58.07	$58.05	$58.10
Purchase #4	$97.99	7.418%	$105.2589	$105.26	$105.25	$105.30
Purchase #5	$198.50	8.732%	$215.833	$215.83	$215.85	$215.80
Purchase #6	$111.99	13.670%	$127.299	$127.30	$127.30	$127.30
Purchase #7	$210.63	13.423%	$238.9029	$238.90	$238.90	$238.90
7 purchase totals =	$834.06		$915.5169	$915.52	$915.55	$915.50