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	$164.94	13.654%	$187.4609	$187.46	$187.45	$187.50
Purchase #2	$154.70	4.225%	$161.2361	$161.24	$161.25	$161.20
Purchase #3	$171.52	9.111%	$187.1472	$187.15	$187.15	$187.10
Purchase #4	$216.44	12.482%	$243.456	$243.46	$243.45	$243.50
Purchase #5	$85.68	6.767%	$91.478	$91.48	$91.50	$91.50
Purchase #6	$249.63	3.506%	$258.382	$258.38	$258.40	$258.40
Purchase #7	$226.64	12.705%	$255.4346	$255.43	$255.45	$255.40
7 purchase totals =	$1,269.55		$1,384.5948	$1,384.60	$1,384.65	$1,384.60