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	$46.31	4.844%	$48.5533	$48.55	$48.55	$48.60
Purchase #2	$159.96	4.121%	$166.552	$166.55	$166.55	$166.60
Purchase #3	$192.55	8.603%	$209.1151	$209.12	$209.10	$209.10
Purchase #4	$47.42	11.403%	$52.8273	$52.83	$52.85	$52.80
Purchase #5	$128.57	13.122%	$145.441	$145.44	$145.45	$145.40
Purchase #6	$197.32	13.181%	$223.3287	$223.33	$223.35	$223.30
Purchase #7	$214.69	4.319%	$223.9625	$223.96	$223.95	$224.00
7 purchase totals =	$986.82		$1,069.7799	$1,069.78	$1,069.80	$1,069.80