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	$102.46	5.558%	$108.1547	$108.15	$108.15	$108.20
Purchase #2	$154.83	6.466%	$164.8413	$164.84	$164.85	$164.80
Purchase #3	$235.91	5.280%	$248.366	$248.37	$248.35	$248.40
Purchase #4	$12.90	5.638%	$13.6273	$13.63	$13.65	$13.60
Purchase #5	$181.59	10.394%	$200.4645	$200.46	$200.45	$200.50
Purchase #6	$37.61	3.255%	$38.8342	$38.83	$38.85	$38.80
Purchase #7	$109.34	10.540%	$120.8644	$120.86	$120.85	$120.90
7 purchase totals =	$834.64		$895.1524	$895.14	$895.15	$895.20