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	$134.81	7.137%	$144.4314	$144.43	$144.45	$144.40
Purchase #2	$146.80	4.470%	$153.362	$153.36	$153.35	$153.40
Purchase #3	$55.47	7.732%	$59.7589	$59.76	$59.75	$59.80
Purchase #4	$51.73	7.498%	$55.6087	$55.61	$55.60	$55.60
Purchase #5	$178.83	5.773%	$189.1539	$189.15	$189.15	$189.20
Purchase #6	$194.44	4.839%	$203.849	$203.85	$203.85	$203.80
Purchase #7	$145.35	11.642%	$162.2716	$162.27	$162.25	$162.30
7 purchase totals =	$907.43		$968.4355	$968.43	$968.40	$968.50