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	$44.48	7.523%	$47.8262	$47.83	$47.85	$47.80
Purchase #2	$19.56	9.379%	$21.3945	$21.39	$21.40	$21.40
Purchase #3	$225.42	12.490%	$253.575	$253.58	$253.60	$253.60
Purchase #4	$90.32	4.418%	$94.3103	$94.31	$94.30	$94.30
Purchase #5	$99.54	13.141%	$112.6206	$112.62	$112.60	$112.60
Purchase #6	$98.62	12.135%	$110.5875	$110.59	$110.60	$110.60
Purchase #7	$144.47	9.750%	$158.5558	$158.56	$158.55	$158.60
7 purchase totals =	$722.41		$798.8699	$798.88	$798.90	$798.90