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	$10.78	9.250%	$11.7772	$11.78	$11.80	$11.80
Purchase #2	$20.88	3.371%	$21.5839	$21.58	$21.60	$21.60
Purchase #3	$179.70	12.588%	$202.3206	$202.32	$202.30	$202.30
Purchase #4	$233.61	4.617%	$244.3958	$244.40	$244.40	$244.40
Purchase #5	$248.48	10.125%	$273.6386	$273.64	$273.65	$273.60
Purchase #6	$224.85	4.153%	$234.188	$234.19	$234.20	$234.20
Purchase #7	$55.83	6.673%	$59.5555	$59.56	$59.55	$59.60
7 purchase totals =	$974.13		$1,047.4596	$1,047.47	$1,047.50	$1,047.50