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	$128.87	13.156%	$145.8241	$145.82	$145.80	$145.80
Purchase #2	$21.61	6.362%	$22.9848	$22.98	$23.00	$23.00
Purchase #3	$39.71	8.292%	$43.0028	$43.00	$43.00	$43.00
Purchase #4	$105.52	6.537%	$112.4178	$112.42	$112.40	$112.40
Purchase #5	$61.78	7.217%	$66.2387	$66.24	$66.25	$66.20
Purchase #6	$28.42	12.672%	$32.0214	$32.02	$32.00	$32.00
Purchase #7	$100.56	4.333%	$104.9173	$104.92	$104.90	$104.90
7 purchase totals =	$486.47		$527.4069	$527.40	$527.35	$527.30