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	$15.75	4.553%	$16.4671	$16.47	$16.45	$16.50
Purchase #2	$39.67	6.765%	$42.3537	$42.35	$42.35	$42.40
Purchase #3	$183.85	6.772%	$196.3003	$196.30	$196.30	$196.30
Purchase #4	$42.74	9.687%	$46.8802	$46.88	$46.90	$46.90
Purchase #5	$59.56	6.613%	$63.4987	$63.50	$63.50	$63.50
Purchase #6	$48.37	12.200%	$54.2711	$54.27	$54.25	$54.30
Purchase #7	$52.86	4.681%	$55.3344	$55.33	$55.35	$55.30
7 purchase totals =	$442.80		$475.1055	$475.10	$475.10	$475.20