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	$201.90	10.564%	$223.2287	$223.23	$223.25	$223.20
Purchase #2	$57.87	13.633%	$65.7594	$65.76	$65.75	$65.80
Purchase #3	$13.39	9.405%	$14.6493	$14.65	$14.65	$14.60
Purchase #4	$129.57	13.548%	$147.1241	$147.12	$147.10	$147.10
Purchase #5	$238.80	7.152%	$255.879	$255.88	$255.90	$255.90
Purchase #6	$125.90	4.729%	$131.8538	$131.85	$131.85	$131.90
Purchase #7	$247.51	10.183%	$272.7139	$272.71	$272.70	$272.70
7 purchase totals =	$1,014.94		$1,111.2082	$1,111.20	$1,111.20	$1,111.20