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	$123.65	6.864%	$132.1373	$132.14	$132.15	$132.10
Purchase #2	$161.52	5.358%	$170.1742	$170.17	$170.15	$170.20
Purchase #3	$28.91	8.236%	$31.291	$31.29	$31.30	$31.30
Purchase #4	$99.68	8.855%	$108.5067	$108.51	$108.50	$108.50
Purchase #5	$214.68	3.652%	$222.5201	$222.52	$222.50	$222.50
Purchase #6	$115.46	4.258%	$120.3763	$120.38	$120.40	$120.40
Purchase #7	$100.66	11.779%	$112.5167	$112.52	$112.50	$112.50
7 purchase totals =	$844.56		$897.5223	$897.53	$897.50	$897.50