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	$221.57	7.250%	$237.6338	$237.63	$237.65	$237.60
Purchase #2	$54.93	3.421%	$56.8092	$56.81	$56.80	$56.80
Purchase #3	$183.58	3.669%	$190.3156	$190.32	$190.30	$190.30
Purchase #4	$163.68	12.453%	$184.0631	$184.06	$184.05	$184.10
Purchase #5	$31.45	4.748%	$32.9432	$32.94	$32.95	$32.90
Purchase #6	$187.87	6.631%	$200.3277	$200.33	$200.35	$200.30
Purchase #7	$208.45	6.412%	$221.8158	$221.82	$221.80	$221.80
7 purchase totals =	$1,051.53		$1,123.9084	$1,123.91	$1,123.90	$1,123.80