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	$130.54	8.317%	$141.397	$141.40	$141.40	$141.40
Purchase #2	$62.96	6.111%	$66.8075	$66.81	$66.80	$66.80
Purchase #3	$174.98	6.650%	$186.6162	$186.62	$186.60	$186.60
Purchase #4	$116.93	8.700%	$127.1029	$127.10	$127.10	$127.10
Purchase #5	$118.93	3.201%	$122.7369	$122.74	$122.75	$122.70
Purchase #6	$54.28	9.225%	$59.2873	$59.29	$59.30	$59.30
Purchase #7	$38.28	12.588%	$43.0987	$43.10	$43.10	$43.10
7 purchase totals =	$696.90		$747.0465	$747.06	$747.05	$747.00