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	$63.87	13.677%	$72.6055	$72.61	$72.60	$72.60
Purchase #2	$52.82	10.794%	$58.5214	$58.52	$58.50	$58.50
Purchase #3	$119.74	9.621%	$131.2602	$131.26	$131.25	$131.30
Purchase #4	$156.53	13.819%	$178.1609	$178.16	$178.15	$178.20
Purchase #5	$45.52	3.449%	$47.09	$47.09	$47.10	$47.10
Purchase #6	$235.46	10.295%	$259.7006	$259.70	$259.70	$259.70
Purchase #7	$53.53	4.276%	$55.8189	$55.82	$55.80	$55.80
7 purchase totals =	$727.47		$803.1575	$803.16	$803.10	$803.20