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	$233.70	4.471%	$244.1487	$244.15	$244.15	$244.10
Purchase #2	$230.63	8.120%	$249.3572	$249.36	$249.35	$249.40
Purchase #3	$246.63	13.681%	$280.3715	$280.37	$280.35	$280.40
Purchase #4	$91.37	9.298%	$99.8656	$99.87	$99.85	$99.90
Purchase #5	$238.58	6.408%	$253.8682	$253.87	$253.85	$253.90
Purchase #6	$63.98	4.685%	$66.9775	$66.98	$67.00	$67.00
Purchase #7	$184.52	13.736%	$209.8657	$209.87	$209.85	$209.90
7 purchase totals =	$1,289.41		$1,404.4544	$1,404.47	$1,404.40	$1,404.60