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	$145.86	11.454%	$162.5668	$162.57	$162.55	$162.60
Purchase #2	$80.70	13.195%	$91.3484	$91.35	$91.35	$91.30
Purchase #3	$153.48	5.823%	$162.4171	$162.42	$162.40	$162.40
Purchase #4	$106.25	3.156%	$109.6033	$109.60	$109.60	$109.60
Purchase #5	$220.77	5.719%	$233.3958	$233.40	$233.40	$233.40
Purchase #6	$172.88	10.158%	$190.4412	$190.44	$190.45	$190.40
Purchase #7	$91.39	13.641%	$103.8565	$103.86	$103.85	$103.90
7 purchase totals =	$971.33		$1,053.6291	$1,053.64	$1,053.60	$1,053.60