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	$50.76	10.434%	$56.0563	$56.06	$56.05	$56.10
Purchase #2	$148.47	6.857%	$158.6506	$158.65	$158.65	$158.70
Purchase #3	$40.57	4.462%	$42.3802	$42.38	$42.40	$42.40
Purchase #4	$165.70	12.206%	$185.9253	$185.93	$185.95	$185.90
Purchase #5	$153.42	4.135%	$159.7639	$159.76	$159.75	$159.80
Purchase #6	$196.40	4.854%	$205.9333	$205.93	$205.95	$205.90
Purchase #7	$246.55	10.287%	$271.9126	$271.91	$271.90	$271.90
7 purchase totals =	$1,001.87		$1,080.6222	$1,080.62	$1,080.65	$1,080.70