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	$131.72	13.160%	$149.0544	$149.05	$149.05	$149.10
Purchase #2	$54.88	7.112%	$58.7831	$58.78	$58.80	$58.80
Purchase #3	$84.80	5.471%	$89.4394	$89.44	$89.45	$89.40
Purchase #4	$132.32	3.823%	$137.3786	$137.38	$137.40	$137.40
Purchase #5	$176.90	10.866%	$196.122	$196.12	$196.10	$196.10
Purchase #6	$80.27	10.803%	$88.9416	$88.94	$88.95	$88.90
Purchase #7	$81.48	6.283%	$86.5994	$86.60	$86.60	$86.60
7 purchase totals =	$742.37		$806.3185	$806.31	$806.35	$806.30