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	$101.48	10.277%	$111.9091	$111.91	$111.90	$111.90
Purchase #2	$182.25	8.528%	$197.7923	$197.79	$197.80	$197.80
Purchase #3	$67.58	7.653%	$72.7519	$72.75	$72.75	$72.80
Purchase #4	$19.41	3.169%	$20.0251	$20.03	$20.05	$20.00
Purchase #5	$228.43	12.351%	$256.6434	$256.64	$256.65	$256.60
Purchase #6	$87.70	4.453%	$91.6053	$91.61	$91.60	$91.60
Purchase #7	$159.67	7.419%	$171.5159	$171.52	$171.50	$171.50
7 purchase totals =	$846.52		$922.2430	$922.25	$922.25	$922.20