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	$78.65	5.419%	$82.912	$82.91	$82.90	$82.90
Purchase #2	$32.92	10.383%	$36.3381	$36.34	$36.35	$36.30
Purchase #3	$51.75	4.825%	$54.2469	$54.25	$54.25	$54.20
Purchase #4	$238.66	9.621%	$261.6215	$261.62	$261.60	$261.60
Purchase #5	$147.46	11.557%	$164.502	$164.50	$164.50	$164.50
Purchase #6	$15.74	6.871%	$16.8215	$16.82	$16.80	$16.80
Purchase #7	$103.91	7.194%	$111.3853	$111.39	$111.40	$111.40
7 purchase totals =	$669.09		$727.8273	$727.83	$727.80	$727.70