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	$217.40	7.409%	$233.5072	$233.51	$233.50	$233.50
Purchase #2	$108.85	6.289%	$115.6956	$115.70	$115.70	$115.70
Purchase #3	$169.46	12.270%	$190.2527	$190.25	$190.25	$190.30
Purchase #4	$43.32	13.235%	$49.0534	$49.05	$49.05	$49.10
Purchase #5	$59.62	9.453%	$65.2559	$65.26	$65.25	$65.30
Purchase #6	$137.37	13.175%	$155.4685	$155.47	$155.45	$155.50
Purchase #7	$99.41	5.139%	$104.5187	$104.52	$104.50	$104.50
7 purchase totals =	$835.43		$913.7520	$913.76	$913.70	$913.90