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	$179.98	10.400%	$198.6979	$198.70	$198.70	$198.70
Purchase #2	$40.39	8.705%	$43.9059	$43.91	$43.90	$43.90
Purchase #3	$168.31	6.854%	$179.846	$179.85	$179.85	$179.80
Purchase #4	$191.28	4.782%	$200.427	$200.43	$200.45	$200.40
Purchase #5	$187.38	12.325%	$210.4746	$210.47	$210.45	$210.50
Purchase #6	$108.29	8.553%	$117.552	$117.55	$117.55	$117.60
Purchase #7	$38.95	10.792%	$43.1535	$43.15	$43.15	$43.20
7 purchase totals =	$914.58		$994.0569	$994.06	$994.05	$994.10