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	$55.89	9.447%	$61.1699	$61.17	$61.15	$61.20
Purchase #2	$171.72	3.806%	$178.2557	$178.26	$178.25	$178.30
Purchase #3	$212.54	8.161%	$229.8854	$229.89	$229.90	$229.90
Purchase #4	$217.28	9.792%	$238.5561	$238.56	$238.55	$238.60
Purchase #5	$23.58	3.366%	$24.3737	$24.37	$24.35	$24.40
Purchase #6	$164.74	6.583%	$175.5848	$175.58	$175.60	$175.60
Purchase #7	$245.42	13.197%	$277.8081	$277.81	$277.80	$277.80
7 purchase totals =	$1,091.17		$1,185.6337	$1,185.64	$1,185.60	$1,185.80