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	$85.32	13.273%	$96.6445	$96.64	$96.65	$96.60
Purchase #2	$136.70	13.682%	$155.4033	$155.40	$155.40	$155.40
Purchase #3	$79.60	12.773%	$89.7673	$89.77	$89.75	$89.80
Purchase #4	$189.51	5.754%	$200.4144	$200.41	$200.40	$200.40
Purchase #5	$49.37	6.857%	$52.7553	$52.76	$52.75	$52.80
Purchase #6	$45.32	6.728%	$48.3691	$48.37	$48.35	$48.40
Purchase #7	$73.29	4.463%	$76.5609	$76.56	$76.55	$76.60
7 purchase totals =	$659.11		$719.9148	$719.91	$719.85	$720.00