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	$230.45	8.803%	$250.7365	$250.74	$250.75	$250.70
Purchase #2	$178.42	4.251%	$186.0046	$186.00	$186.00	$186.00
Purchase #3	$158.45	9.497%	$173.498	$173.50	$173.50	$173.50
Purchase #4	$38.85	9.668%	$42.606	$42.61	$42.60	$42.60
Purchase #5	$125.54	6.447%	$133.6336	$133.63	$133.65	$133.60
Purchase #6	$174.81	11.732%	$195.3187	$195.32	$195.30	$195.30
Purchase #7	$39.41	10.189%	$43.4255	$43.43	$43.45	$43.40
7 purchase totals =	$945.93		$1,025.2229	$1,025.23	$1,025.25	$1,025.10