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	$226.84	4.146%	$236.2448	$236.24	$236.25	$236.20
Purchase #2	$115.71	6.686%	$123.4464	$123.45	$123.45	$123.40
Purchase #3	$154.79	3.353%	$159.9801	$159.98	$160.00	$160.00
Purchase #4	$94.90	6.326%	$100.9034	$100.90	$100.90	$100.90
Purchase #5	$133.31	13.209%	$150.9189	$150.92	$150.90	$150.90
Purchase #6	$249.59	13.331%	$282.8628	$282.86	$282.85	$282.90
Purchase #7	$221.43	12.373%	$248.8275	$248.83	$248.85	$248.80
7 purchase totals =	$1,196.57		$1,303.1839	$1,303.18	$1,303.20	$1,303.10