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	$63.94	13.824%	$72.7791	$72.78	$72.80	$72.80
Purchase #2	$87.46	10.645%	$96.7701	$96.77	$96.75	$96.80
Purchase #3	$249.54	3.630%	$258.5983	$258.60	$258.60	$258.60
Purchase #4	$96.67	6.365%	$102.823	$102.82	$102.80	$102.80
Purchase #5	$186.70	10.251%	$205.8386	$205.84	$205.85	$205.80
Purchase #6	$246.91	3.564%	$255.7099	$255.71	$255.70	$255.70
Purchase #7	$106.96	5.578%	$112.9262	$112.93	$112.95	$112.90
7 purchase totals =	$1,038.18		$1,105.4452	$1,105.45	$1,105.45	$1,105.40