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	$13.75	5.767%	$14.543	$14.54	$14.55	$14.50
Purchase #2	$101.55	13.699%	$115.4613	$115.46	$115.45	$115.50
Purchase #3	$89.56	13.305%	$101.476	$101.48	$101.50	$101.50
Purchase #4	$158.89	4.654%	$166.2847	$166.28	$166.30	$166.30
Purchase #5	$102.89	10.777%	$113.9785	$113.98	$114.00	$114.00
Purchase #6	$77.74	6.492%	$82.7869	$82.79	$82.80	$82.80
Purchase #7	$38.60	9.331%	$42.2018	$42.20	$42.20	$42.20
7 purchase totals =	$582.98		$636.7322	$636.73	$636.80	$636.80