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	$52.93	5.469%	$55.8247	$55.82	$55.80	$55.80
Purchase #2	$106.47	5.329%	$112.1438	$112.14	$112.15	$112.10
Purchase #3	$87.55	11.716%	$97.8074	$97.81	$97.80	$97.80
Purchase #4	$71.93	6.369%	$76.5112	$76.51	$76.50	$76.50
Purchase #5	$21.73	5.145%	$22.848	$22.85	$22.85	$22.80
Purchase #6	$118.72	7.540%	$127.6715	$127.67	$127.65	$127.70
Purchase #7	$68.79	12.647%	$77.4899	$77.49	$77.50	$77.50
7 purchase totals =	$528.12		$570.2965	$570.29	$570.25	$570.20