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	$103.48	11.218%	$115.0884	$115.09	$115.10	$115.10
Purchase #2	$158.50	12.243%	$177.9052	$177.91	$177.90	$177.90
Purchase #3	$159.51	3.816%	$165.5969	$165.60	$165.60	$165.60
Purchase #4	$144.32	8.533%	$156.6348	$156.63	$156.65	$156.60
Purchase #5	$50.34	8.181%	$54.4583	$54.46	$54.45	$54.50
Purchase #6	$53.75	9.828%	$59.0326	$59.03	$59.05	$59.00
Purchase #7	$133.76	10.740%	$148.1258	$148.13	$148.15	$148.10
7 purchase totals =	$803.66		$876.8420	$876.85	$876.90	$876.80