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	$158.61	7.520%	$170.5375	$170.54	$170.55	$170.50
Purchase #2	$182.97	4.795%	$191.7434	$191.74	$191.75	$191.70
Purchase #3	$148.64	9.172%	$162.2733	$162.27	$162.25	$162.30
Purchase #4	$108.38	3.623%	$112.3066	$112.31	$112.30	$112.30
Purchase #5	$54.43	3.236%	$56.1914	$56.19	$56.20	$56.20
Purchase #6	$64.42	4.475%	$67.3028	$67.30	$67.30	$67.30
Purchase #7	$188.29	9.170%	$205.5562	$205.56	$205.55	$205.60
7 purchase totals =	$905.74		$965.9112	$965.91	$965.90	$965.90