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	$193.33	11.843%	$216.2261	$216.23	$216.25	$216.20
Purchase #2	$137.26	3.682%	$142.3139	$142.31	$142.30	$142.30
Purchase #3	$74.49	3.812%	$77.3296	$77.33	$77.35	$77.30
Purchase #4	$238.58	6.716%	$254.603	$254.60	$254.60	$254.60
Purchase #5	$86.45	9.375%	$94.5547	$94.55	$94.55	$94.60
Purchase #6	$39.82	5.863%	$42.1546	$42.15	$42.15	$42.20
Purchase #7	$92.54	10.582%	$102.3326	$102.33	$102.35	$102.30
7 purchase totals =	$862.47		$929.5145	$929.50	$929.55	$929.50