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	$145.94	8.422%	$158.2311	$158.23	$158.25	$158.20
Purchase #2	$75.86	8.503%	$82.3104	$82.31	$82.30	$82.30
Purchase #3	$228.37	11.780%	$255.272	$255.27	$255.25	$255.30
Purchase #4	$236.89	6.864%	$253.1501	$253.15	$253.15	$253.20
Purchase #5	$59.28	3.481%	$61.3435	$61.34	$61.35	$61.30
Purchase #6	$186.64	9.508%	$204.3857	$204.39	$204.40	$204.40
Purchase #7	$75.95	10.683%	$84.0637	$84.06	$84.05	$84.10
7 purchase totals =	$1,008.93		$1,098.7565	$1,098.75	$1,098.75	$1,098.80