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	$211.99	3.551%	$219.5178	$219.52	$219.50	$219.50
Purchase #2	$54.33	5.861%	$57.5143	$57.51	$57.50	$57.50
Purchase #3	$45.52	10.147%	$50.1389	$50.14	$50.15	$50.10
Purchase #4	$49.28	8.812%	$53.6226	$53.62	$53.60	$53.60
Purchase #5	$102.81	8.400%	$111.446	$111.45	$111.45	$111.40
Purchase #6	$41.85	5.814%	$44.2832	$44.28	$44.30	$44.30
Purchase #7	$61.37	11.418%	$68.3772	$68.38	$68.40	$68.40
7 purchase totals =	$567.15		$604.9000	$604.90	$604.90	$604.80