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	$67.60	10.556%	$74.7359	$74.74	$74.75	$74.70
Purchase #2	$121.54	4.813%	$127.3897	$127.39	$127.40	$127.40
Purchase #3	$239.29	8.670%	$260.0364	$260.04	$260.05	$260.00
Purchase #4	$42.66	10.524%	$47.1495	$47.15	$47.15	$47.10
Purchase #5	$37.52	13.275%	$42.5008	$42.50	$42.50	$42.50
Purchase #6	$248.64	12.724%	$280.277	$280.28	$280.30	$280.30
Purchase #7	$178.50	3.759%	$185.2098	$185.21	$185.20	$185.20
7 purchase totals =	$935.75		$1,017.2991	$1,017.31	$1,017.35	$1,017.20