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	$220.86	3.476%	$228.5371	$228.54	$228.55	$228.50
Purchase #2	$102.69	11.830%	$114.8382	$114.84	$114.85	$114.80
Purchase #3	$198.77	10.573%	$219.786	$219.79	$219.80	$219.80
Purchase #4	$76.85	8.403%	$83.3077	$83.31	$83.30	$83.30
Purchase #5	$202.49	11.328%	$225.4281	$225.43	$225.45	$225.40
Purchase #6	$96.42	4.587%	$100.8428	$100.84	$100.85	$100.80
Purchase #7	$48.71	8.777%	$52.9853	$52.99	$53.00	$53.00
7 purchase totals =	$946.79		$1,025.7252	$1,025.74	$1,025.80	$1,025.60