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	$63.71	4.156%	$66.3578	$66.36	$66.35	$66.40
Purchase #2	$181.37	8.501%	$196.7883	$196.79	$196.80	$196.80
Purchase #3	$172.74	10.651%	$191.1385	$191.14	$191.15	$191.10
Purchase #4	$154.30	6.661%	$164.5779	$164.58	$164.60	$164.60
Purchase #5	$187.88	6.541%	$200.1692	$200.17	$200.15	$200.20
Purchase #6	$110.27	3.409%	$114.0291	$114.03	$114.05	$114.00
Purchase #7	$82.25	4.631%	$86.059	$86.06	$86.05	$86.10
7 purchase totals =	$952.52		$1,019.1198	$1,019.13	$1,019.15	$1,019.20