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	$10.69	8.459%	$11.5943	$11.59	$11.60	$11.60
Purchase #2	$77.78	7.623%	$83.7092	$83.71	$83.70	$83.70
Purchase #3	$167.72	10.444%	$185.2367	$185.24	$185.25	$185.20
Purchase #4	$146.91	9.203%	$160.4301	$160.43	$160.45	$160.40
Purchase #5	$158.80	10.187%	$174.977	$174.98	$175.00	$175.00
Purchase #6	$133.67	9.546%	$146.4301	$146.43	$146.45	$146.40
Purchase #7	$223.42	13.293%	$253.1192	$253.12	$253.10	$253.10
7 purchase totals =	$918.99		$1,015.4966	$1,015.50	$1,015.55	$1,015.40