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	$123.60	5.351%	$130.2138	$130.21	$130.20	$130.20
Purchase #2	$38.85	3.704%	$40.289	$40.29	$40.30	$40.30
Purchase #3	$178.83	12.180%	$200.6115	$200.61	$200.60	$200.60
Purchase #4	$214.83	12.305%	$241.2648	$241.26	$241.25	$241.30
Purchase #5	$149.55	8.868%	$162.8121	$162.81	$162.80	$162.80
Purchase #6	$100.29	9.616%	$109.9339	$109.93	$109.95	$109.90
Purchase #7	$161.61	11.350%	$179.9527	$179.95	$179.95	$180.00
7 purchase totals =	$967.56		$1,065.0778	$1,065.06	$1,065.05	$1,065.10