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	$109.90	9.560%	$120.4064	$120.41	$120.40	$120.40
Purchase #2	$215.95	6.657%	$230.3258	$230.33	$230.35	$230.30
Purchase #3	$34.46	11.325%	$38.3626	$38.36	$38.35	$38.40
Purchase #4	$65.75	7.682%	$70.8009	$70.80	$70.80	$70.80
Purchase #5	$187.81	9.397%	$205.4585	$205.46	$205.45	$205.50
Purchase #6	$78.31	10.156%	$86.2632	$86.26	$86.25	$86.30
Purchase #7	$243.72	9.680%	$267.3121	$267.31	$267.30	$267.30
7 purchase totals =	$935.90		$1,018.9295	$1,018.93	$1,018.90	$1,019.00