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	$46.64	8.661%	$50.6795	$50.68	$50.70	$50.70
Purchase #2	$199.55	6.623%	$212.7662	$212.77	$212.75	$212.80
Purchase #3	$240.88	10.622%	$266.4663	$266.47	$266.45	$266.50
Purchase #4	$94.86	12.335%	$106.561	$106.56	$106.55	$106.60
Purchase #5	$140.56	12.839%	$158.6065	$158.61	$158.60	$158.60
Purchase #6	$136.91	3.633%	$141.8839	$141.88	$141.90	$141.90
Purchase #7	$173.37	7.557%	$186.4716	$186.47	$186.45	$186.50
7 purchase totals =	$1,032.77		$1,123.4350	$1,123.44	$1,123.40	$1,123.60