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	$117.43	4.858%	$123.1347	$123.13	$123.15	$123.10
Purchase #2	$114.72	7.430%	$123.2437	$123.24	$123.25	$123.20
Purchase #3	$56.92	3.165%	$58.7215	$58.72	$58.70	$58.70
Purchase #4	$172.45	10.446%	$190.4641	$190.46	$190.45	$190.50
Purchase #5	$188.83	13.353%	$214.0445	$214.04	$214.05	$214.00
Purchase #6	$58.44	7.642%	$62.906	$62.91	$62.90	$62.90
Purchase #7	$111.62	10.491%	$123.3301	$123.33	$123.35	$123.30
7 purchase totals =	$820.41		$895.8446	$895.83	$895.85	$895.70