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	$169.83	11.785%	$189.8445	$189.84	$189.85	$189.80
Purchase #2	$242.87	9.868%	$266.8364	$266.84	$266.85	$266.80
Purchase #3	$130.80	5.138%	$137.5205	$137.52	$137.50	$137.50
Purchase #4	$111.31	7.333%	$119.4724	$119.47	$119.45	$119.50
Purchase #5	$150.50	9.628%	$164.9901	$164.99	$165.00	$165.00
Purchase #6	$191.99	10.562%	$212.268	$212.27	$212.25	$212.30
Purchase #7	$29.72	9.207%	$32.4563	$32.46	$32.45	$32.50
7 purchase totals =	$1,027.02		$1,123.3882	$1,123.39	$1,123.35	$1,123.40