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	$115.88	10.285%	$127.7983	$127.80	$127.80	$127.80
Purchase #2	$55.57	7.243%	$59.5949	$59.59	$59.60	$59.60
Purchase #3	$214.61	9.181%	$234.3133	$234.31	$234.30	$234.30
Purchase #4	$137.47	13.654%	$156.2402	$156.24	$156.25	$156.20
Purchase #5	$30.55	6.153%	$32.4297	$32.43	$32.45	$32.40
Purchase #6	$17.54	7.807%	$18.9093	$18.91	$18.90	$18.90
Purchase #7	$20.90	10.240%	$23.0402	$23.04	$23.05	$23.00
7 purchase totals =	$592.52		$652.3259	$652.32	$652.35	$652.20