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	$98.86	12.766%	$111.4805	$111.48	$111.50	$111.50
Purchase #2	$40.60	5.243%	$42.7287	$42.73	$42.75	$42.70
Purchase #3	$221.70	10.285%	$244.5018	$244.50	$244.50	$244.50
Purchase #4	$145.67	4.766%	$152.6126	$152.61	$152.60	$152.60
Purchase #5	$194.34	6.238%	$206.4629	$206.46	$206.45	$206.50
Purchase #6	$149.67	7.404%	$160.7516	$160.75	$160.75	$160.80
Purchase #7	$163.33	12.126%	$183.1354	$183.14	$183.15	$183.10
7 purchase totals =	$1,014.17		$1,101.6735	$1,101.67	$1,101.70	$1,101.70