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	$222.53	9.155%	$242.9026	$242.90	$242.90	$242.90
Purchase #2	$11.39	8.587%	$12.3681	$12.37	$12.35	$12.40
Purchase #3	$103.89	10.477%	$114.7746	$114.77	$114.75	$114.80
Purchase #4	$183.31	13.560%	$208.1668	$208.17	$208.15	$208.20
Purchase #5	$133.41	12.670%	$150.313	$150.31	$150.30	$150.30
Purchase #6	$165.97	13.346%	$188.1204	$188.12	$188.10	$188.10
Purchase #7	$114.90	10.687%	$127.1794	$127.18	$127.20	$127.20
7 purchase totals =	$935.40		$1,043.8249	$1,043.82	$1,043.75	$1,043.90