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	$182.45	4.609%	$190.8591	$190.86	$190.85	$190.90
Purchase #2	$81.81	9.546%	$89.6196	$89.62	$89.60	$89.60
Purchase #3	$74.53	4.390%	$77.8019	$77.80	$77.80	$77.80
Purchase #4	$11.71	12.390%	$13.1609	$13.16	$13.15	$13.20
Purchase #5	$72.46	9.231%	$79.1488	$79.15	$79.15	$79.10
Purchase #6	$68.46	11.650%	$76.4356	$76.44	$76.45	$76.40
Purchase #7	$196.38	9.795%	$215.6154	$215.62	$215.60	$215.60
7 purchase totals =	$687.80		$742.6413	$742.65	$742.60	$742.60