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	$107.53	4.657%	$112.5377	$112.54	$112.55	$112.50
Purchase #2	$202.52	4.844%	$212.3301	$212.33	$212.35	$212.30
Purchase #3	$190.70	13.193%	$215.8591	$215.86	$215.85	$215.90
Purchase #4	$76.29	5.250%	$80.2952	$80.30	$80.30	$80.30
Purchase #5	$30.77	12.447%	$34.5999	$34.60	$34.60	$34.60
Purchase #6	$221.78	7.687%	$238.8282	$238.83	$238.85	$238.80
Purchase #7	$240.50	8.686%	$261.3898	$261.39	$261.40	$261.40
7 purchase totals =	$1,070.09		$1,155.8400	$1,155.85	$1,155.90	$1,155.80