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	$85.46	10.601%	$94.5196	$94.52	$94.50	$94.50
Purchase #2	$107.71	9.851%	$118.3205	$118.32	$118.30	$118.30
Purchase #3	$154.75	13.624%	$175.8331	$175.83	$175.85	$175.80
Purchase #4	$223.82	10.299%	$246.8712	$246.87	$246.85	$246.90
Purchase #5	$210.62	11.515%	$234.8729	$234.87	$234.85	$234.90
Purchase #6	$213.40	11.593%	$238.1395	$238.14	$238.15	$238.10
Purchase #7	$101.25	4.209%	$105.5116	$105.51	$105.50	$105.50
7 purchase totals =	$1,097.01		$1,214.0684	$1,214.06	$1,214.00	$1,214.00