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	$204.35	12.244%	$229.3706	$229.37	$229.35	$229.40
Purchase #2	$218.69	3.263%	$225.8259	$225.83	$225.85	$225.80
Purchase #3	$77.54	6.515%	$82.5917	$82.59	$82.60	$82.60
Purchase #4	$146.27	5.772%	$154.7127	$154.71	$154.70	$154.70
Purchase #5	$62.27	13.141%	$70.4529	$70.45	$70.45	$70.50
Purchase #6	$104.50	9.564%	$114.4944	$114.49	$114.50	$114.50
Purchase #7	$197.61	8.868%	$215.1341	$215.13	$215.15	$215.10
7 purchase totals =	$1,011.23		$1,092.5823	$1,092.57	$1,092.60	$1,092.60