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	$245.73	9.468%	$268.9957	$269.00	$269.00	$269.00
Purchase #2	$213.63	4.369%	$222.9635	$222.96	$222.95	$223.00
Purchase #3	$158.60	5.171%	$166.8012	$166.80	$166.80	$166.80
Purchase #4	$77.36	6.551%	$82.4279	$82.43	$82.45	$82.40
Purchase #5	$14.99	13.799%	$17.0585	$17.06	$17.05	$17.10
Purchase #6	$116.43	10.375%	$128.5096	$128.51	$128.50	$128.50
Purchase #7	$188.73	6.269%	$200.5615	$200.56	$200.55	$200.60
7 purchase totals =	$1,015.47		$1,087.3179	$1,087.32	$1,087.30	$1,087.40