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	$106.90	4.213%	$111.4037	$111.40	$111.40	$111.40
Purchase #2	$109.77	6.381%	$116.7744	$116.77	$116.75	$116.80
Purchase #3	$101.78	5.444%	$107.3209	$107.32	$107.30	$107.30
Purchase #4	$225.75	13.302%	$255.7793	$255.78	$255.80	$255.80
Purchase #5	$143.57	5.253%	$151.1117	$151.11	$151.10	$151.10
Purchase #6	$142.82	9.585%	$156.5093	$156.51	$156.50	$156.50
Purchase #7	$77.47	11.815%	$86.6231	$86.62	$86.60	$86.60
7 purchase totals =	$908.06		$985.5224	$985.51	$985.45	$985.50