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	$242.70	3.510%	$251.2188	$251.22	$251.20	$251.20
Purchase #2	$52.74	13.183%	$59.6927	$59.69	$59.70	$59.70
Purchase #3	$158.79	12.188%	$178.1433	$178.14	$178.15	$178.10
Purchase #4	$167.81	8.498%	$182.0705	$182.07	$182.05	$182.10
Purchase #5	$220.71	11.233%	$245.5024	$245.50	$245.50	$245.50
Purchase #6	$119.52	12.235%	$134.1433	$134.14	$134.15	$134.10
Purchase #7	$184.28	11.535%	$205.5367	$205.54	$205.55	$205.50
7 purchase totals =	$1,146.55		$1,256.3077	$1,256.30	$1,256.30	$1,256.20