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	$206.97	6.577%	$220.5824	$220.58	$220.60	$220.60
Purchase #2	$104.53	6.783%	$111.6203	$111.62	$111.60	$111.60
Purchase #3	$104.80	13.220%	$118.6546	$118.65	$118.65	$118.70
Purchase #4	$187.49	6.252%	$199.2119	$199.21	$199.20	$199.20
Purchase #5	$42.76	10.136%	$47.0942	$47.09	$47.10	$47.10
Purchase #6	$202.82	9.478%	$222.0433	$222.04	$222.05	$222.00
Purchase #7	$104.64	6.596%	$111.5421	$111.54	$111.55	$111.50
7 purchase totals =	$954.01		$1,030.7488	$1,030.73	$1,030.75	$1,030.70