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	$53.71	13.677%	$61.0559	$61.06	$61.05	$61.10
Purchase #2	$27.74	12.404%	$31.1809	$31.18	$31.20	$31.20
Purchase #3	$15.34	11.252%	$17.0661	$17.07	$17.05	$17.10
Purchase #4	$78.55	11.858%	$87.8645	$87.86	$87.85	$87.90
Purchase #5	$175.61	8.238%	$190.0768	$190.08	$190.10	$190.10
Purchase #6	$64.94	4.324%	$67.748	$67.75	$67.75	$67.70
Purchase #7	$70.50	10.513%	$77.9117	$77.91	$77.90	$77.90
7 purchase totals =	$486.39		$532.9039	$532.91	$532.90	$533.00