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	$143.70	4.741%	$150.5128	$150.51	$150.50	$150.50
Purchase #2	$173.71	3.804%	$180.3179	$180.32	$180.30	$180.30
Purchase #3	$179.57	5.122%	$188.7676	$188.77	$188.75	$188.80
Purchase #4	$188.43	3.250%	$194.554	$194.55	$194.55	$194.60
Purchase #5	$48.32	10.724%	$53.5018	$53.50	$53.50	$53.50
Purchase #6	$116.55	5.658%	$123.1444	$123.14	$123.15	$123.10
Purchase #7	$218.48	4.445%	$228.1914	$228.19	$228.20	$228.20
7 purchase totals =	$1,068.76		$1,118.9899	$1,118.98	$1,118.95	$1,119.00