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	$154.90	5.153%	$162.882	$162.88	$162.90	$162.90
Purchase #2	$75.84	12.628%	$85.4171	$85.42	$85.40	$85.40
Purchase #3	$159.72	5.543%	$168.5733	$168.57	$168.55	$168.60
Purchase #4	$13.55	7.834%	$14.6115	$14.61	$14.60	$14.60
Purchase #5	$205.87	9.128%	$224.6618	$224.66	$224.65	$224.70
Purchase #6	$50.78	6.836%	$54.2513	$54.25	$54.25	$54.30
Purchase #7	$174.90	10.115%	$192.5911	$192.59	$192.60	$192.60
7 purchase totals =	$835.56		$902.9881	$902.98	$902.95	$903.10