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	$52.68	10.725%	$58.3299	$58.33	$58.35	$58.30
Purchase #2	$176.47	13.762%	$200.7558	$200.76	$200.75	$200.80
Purchase #3	$105.81	8.157%	$114.4409	$114.44	$114.45	$114.40
Purchase #4	$40.70	13.581%	$46.2275	$46.23	$46.25	$46.20
Purchase #5	$113.86	12.183%	$127.7316	$127.73	$127.75	$127.70
Purchase #6	$80.42	5.102%	$84.523	$84.52	$84.50	$84.50
Purchase #7	$151.29	3.333%	$156.3325	$156.33	$156.35	$156.30
7 purchase totals =	$721.23		$788.3412	$788.34	$788.40	$788.20