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	$31.48	3.419%	$32.5563	$32.56	$32.55	$32.60
Purchase #2	$161.38	6.554%	$171.9568	$171.96	$171.95	$172.00
Purchase #3	$102.45	12.419%	$115.1733	$115.17	$115.15	$115.20
Purchase #4	$168.90	9.287%	$184.5857	$184.59	$184.60	$184.60
Purchase #5	$173.37	12.408%	$194.8817	$194.88	$194.90	$194.90
Purchase #6	$61.81	6.476%	$65.8128	$65.81	$65.80	$65.80
Purchase #7	$106.91	10.677%	$118.3248	$118.32	$118.30	$118.30
7 purchase totals =	$806.30		$883.2914	$883.29	$883.25	$883.40