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	$123.29	3.705%	$127.8579	$127.86	$127.85	$127.90
Purchase #2	$154.77	6.634%	$165.0374	$165.04	$165.05	$165.00
Purchase #3	$250.55	4.592%	$262.0553	$262.06	$262.05	$262.10
Purchase #4	$185.27	9.718%	$203.2745	$203.27	$203.25	$203.30
Purchase #5	$42.56	8.533%	$46.1916	$46.19	$46.20	$46.20
Purchase #6	$174.44	3.442%	$180.4442	$180.44	$180.45	$180.40
Purchase #7	$76.56	7.211%	$82.0807	$82.08	$82.10	$82.10
7 purchase totals =	$1,007.44		$1,066.9416	$1,066.94	$1,066.95	$1,067.00