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	$187.36	4.837%	$196.4226	$196.42	$196.40	$196.40
Purchase #2	$238.29	10.710%	$263.8109	$263.81	$263.80	$263.80
Purchase #3	$128.29	8.620%	$139.3486	$139.35	$139.35	$139.30
Purchase #4	$89.40	11.401%	$99.5925	$99.59	$99.60	$99.60
Purchase #5	$226.93	5.722%	$239.9149	$239.91	$239.90	$239.90
Purchase #6	$134.42	13.261%	$152.2454	$152.25	$152.25	$152.20
Purchase #7	$160.41	4.555%	$167.7167	$167.72	$167.70	$167.70
7 purchase totals =	$1,165.10		$1,259.0516	$1,259.05	$1,259.00	$1,258.90