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	$141.35	10.237%	$155.82	$155.82	$155.80	$155.80
Purchase #2	$32.80	11.784%	$36.6652	$36.67	$36.65	$36.70
Purchase #3	$236.82	7.647%	$254.9296	$254.93	$254.95	$254.90
Purchase #4	$97.73	4.348%	$101.9793	$101.98	$102.00	$102.00
Purchase #5	$186.92	7.176%	$200.3334	$200.33	$200.35	$200.30
Purchase #6	$49.58	7.622%	$53.359	$53.36	$53.35	$53.40
Purchase #7	$89.82	11.484%	$100.1349	$100.13	$100.15	$100.10
7 purchase totals =	$835.02		$903.2214	$903.22	$903.25	$903.20