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	$86.66	3.587%	$89.7685	$89.77	$89.75	$89.80
Purchase #2	$66.50	9.199%	$72.6173	$72.62	$72.60	$72.60
Purchase #3	$190.33	12.604%	$214.3192	$214.32	$214.30	$214.30
Purchase #4	$239.75	7.639%	$258.0645	$258.06	$258.05	$258.10
Purchase #5	$244.95	13.763%	$278.6625	$278.66	$278.65	$278.70
Purchase #6	$183.32	6.118%	$194.5355	$194.54	$194.55	$194.50
Purchase #7	$46.74	7.854%	$50.411	$50.41	$50.40	$50.40
7 purchase totals =	$1,058.25		$1,158.3785	$1,158.38	$1,158.30	$1,158.40