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	$177.32	13.268%	$200.8468	$200.85	$200.85	$200.80
Purchase #2	$71.87	10.359%	$79.315	$79.32	$79.30	$79.30
Purchase #3	$79.58	5.313%	$83.8081	$83.81	$83.80	$83.80
Purchase #4	$213.91	10.301%	$235.9449	$235.94	$235.95	$235.90
Purchase #5	$191.84	10.405%	$211.801	$211.80	$211.80	$211.80
Purchase #6	$211.60	6.546%	$225.4513	$225.45	$225.45	$225.50
Purchase #7	$80.38	7.444%	$86.3635	$86.36	$86.35	$86.40
7 purchase totals =	$1,026.50		$1,123.5306	$1,123.53	$1,123.50	$1,123.50