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	$49.51	11.179%	$55.0447	$55.04	$55.05	$55.00
Purchase #2	$130.29	11.587%	$145.3867	$145.39	$145.40	$145.40
Purchase #3	$119.54	5.532%	$126.153	$126.15	$126.15	$126.20
Purchase #4	$244.33	7.360%	$262.3127	$262.31	$262.30	$262.30
Purchase #5	$144.91	6.463%	$154.2755	$154.28	$154.30	$154.30
Purchase #6	$78.57	3.467%	$81.294	$81.29	$81.30	$81.30
Purchase #7	$238.49	6.680%	$254.4211	$254.42	$254.40	$254.40
7 purchase totals =	$1,005.64		$1,078.8877	$1,078.88	$1,078.90	$1,078.90