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	$19.91	12.513%	$22.4013	$22.40	$22.40	$22.40
Purchase #2	$183.74	3.192%	$189.605	$189.61	$189.60	$189.60
Purchase #3	$84.29	6.305%	$89.6045	$89.60	$89.60	$89.60
Purchase #4	$49.50	4.135%	$51.5468	$51.55	$51.55	$51.50
Purchase #5	$160.89	10.301%	$177.4633	$177.46	$177.45	$177.50
Purchase #6	$222.27	3.797%	$230.7096	$230.71	$230.70	$230.70
Purchase #7	$247.67	6.808%	$264.5314	$264.53	$264.55	$264.50
7 purchase totals =	$968.27		$1,025.8619	$1,025.86	$1,025.85	$1,025.80