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	$212.31	10.103%	$233.7597	$233.76	$233.75	$233.80
Purchase #2	$144.89	9.493%	$158.6444	$158.64	$158.65	$158.60
Purchase #3	$51.91	13.854%	$59.1016	$59.10	$59.10	$59.10
Purchase #4	$71.28	10.333%	$78.6454	$78.65	$78.65	$78.60
Purchase #5	$6.84	3.633%	$7.0885	$7.09	$7.10	$7.10
Purchase #6	$212.26	8.184%	$229.6314	$229.63	$229.65	$229.60
Purchase #7	$171.72	9.444%	$187.9372	$187.94	$187.95	$187.90
7 purchase totals =	$871.21		$954.8082	$954.81	$954.85	$954.70