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	$12.63	9.702%	$13.8554	$13.86	$13.85	$13.90
Purchase #2	$157.63	4.770%	$165.149	$165.15	$165.15	$165.10
Purchase #3	$122.32	6.712%	$130.5301	$130.53	$130.55	$130.50
Purchase #4	$25.89	10.356%	$28.5712	$28.57	$28.55	$28.60
Purchase #5	$240.32	6.405%	$255.7125	$255.71	$255.70	$255.70
Purchase #6	$226.81	10.865%	$251.4529	$251.45	$251.45	$251.50
Purchase #7	$66.51	4.109%	$69.2429	$69.24	$69.25	$69.20
7 purchase totals =	$852.11		$914.5140	$914.51	$914.50	$914.50