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	$106.31	6.810%	$113.5497	$113.55	$113.55	$113.50
Purchase #2	$152.64	9.716%	$167.4705	$167.47	$167.45	$167.50
Purchase #3	$90.84	11.722%	$101.4883	$101.49	$101.50	$101.50
Purchase #4	$168.98	12.749%	$190.5233	$190.52	$190.50	$190.50
Purchase #5	$205.88	13.844%	$234.382	$234.38	$234.40	$234.40
Purchase #6	$204.46	7.329%	$219.4449	$219.44	$219.45	$219.40
Purchase #7	$98.90	4.176%	$103.0301	$103.03	$103.05	$103.00
7 purchase totals =	$1,028.01		$1,129.8888	$1,129.88	$1,129.90	$1,129.80