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	$196.28	6.416%	$208.8733	$208.87	$208.85	$208.90
Purchase #2	$49.60	13.522%	$56.3069	$56.31	$56.30	$56.30
Purchase #3	$235.75	8.532%	$255.8642	$255.86	$255.85	$255.90
Purchase #4	$228.92	12.710%	$258.0157	$258.02	$258.00	$258.00
Purchase #5	$39.40	5.452%	$41.5481	$41.55	$41.55	$41.50
Purchase #6	$82.42	8.365%	$89.3144	$89.31	$89.30	$89.30
Purchase #7	$150.62	10.574%	$166.5466	$166.55	$166.55	$166.50
7 purchase totals =	$982.99		$1,076.4692	$1,076.47	$1,076.40	$1,076.40