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	$96.51	10.471%	$106.6156	$106.62	$106.60	$106.60
Purchase #2	$55.71	11.845%	$62.3088	$62.31	$62.30	$62.30
Purchase #3	$138.28	10.323%	$152.5546	$152.55	$152.55	$152.60
Purchase #4	$219.45	4.122%	$228.4957	$228.50	$228.50	$228.50
Purchase #5	$219.93	9.873%	$241.6437	$241.64	$241.65	$241.60
Purchase #6	$139.45	9.799%	$153.1147	$153.11	$153.10	$153.10
Purchase #7	$150.92	10.259%	$166.4029	$166.40	$166.40	$166.40
7 purchase totals =	$1,020.25		$1,111.1360	$1,111.13	$1,111.10	$1,111.10