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	$184.72	3.563%	$191.3016	$191.30	$191.30	$191.30
Purchase #2	$139.82	3.457%	$144.6536	$144.65	$144.65	$144.70
Purchase #3	$37.64	4.802%	$39.4475	$39.45	$39.45	$39.40
Purchase #4	$134.88	4.353%	$140.7513	$140.75	$140.75	$140.80
Purchase #5	$64.49	12.106%	$72.2972	$72.30	$72.30	$72.30
Purchase #6	$238.54	11.832%	$266.7641	$266.76	$266.75	$266.80
Purchase #7	$165.67	4.790%	$173.6056	$173.61	$173.60	$173.60
7 purchase totals =	$965.76		$1,028.8209	$1,028.82	$1,028.80	$1,028.90