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	$153.66	4.707%	$160.8928	$160.89	$160.90	$160.90
Purchase #2	$107.30	9.102%	$117.0664	$117.07	$117.05	$117.10
Purchase #3	$137.80	3.474%	$142.5872	$142.59	$142.60	$142.60
Purchase #4	$239.40	12.429%	$269.155	$269.16	$269.15	$269.20
Purchase #5	$100.88	13.862%	$114.864	$114.86	$114.85	$114.90
Purchase #6	$59.52	6.144%	$63.1769	$63.18	$63.20	$63.20
Purchase #7	$127.55	10.317%	$140.7093	$140.71	$140.70	$140.70
7 purchase totals =	$926.11		$1,008.4516	$1,008.46	$1,008.45	$1,008.60