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	$105.64	3.865%	$109.723	$109.72	$109.70	$109.70
Purchase #2	$141.34	13.247%	$160.0633	$160.06	$160.05	$160.10
Purchase #3	$105.85	5.238%	$111.3944	$111.39	$111.40	$111.40
Purchase #4	$143.75	13.123%	$162.6143	$162.61	$162.60	$162.60
Purchase #5	$70.30	11.849%	$78.6298	$78.63	$78.65	$78.60
Purchase #6	$183.66	6.574%	$195.7338	$195.73	$195.75	$195.70
Purchase #7	$107.84	6.137%	$114.4581	$114.46	$114.45	$114.50
7 purchase totals =	$858.38		$932.6167	$932.60	$932.60	$932.60