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	$99.85	11.374%	$111.2069	$111.21	$111.20	$111.20
Purchase #2	$84.87	13.403%	$96.2451	$96.25	$96.25	$96.20
Purchase #3	$43.67	12.146%	$48.9742	$48.97	$48.95	$49.00
Purchase #4	$229.56	12.345%	$257.8992	$257.90	$257.90	$257.90
Purchase #5	$138.91	10.410%	$153.3705	$153.37	$153.35	$153.40
Purchase #6	$53.65	11.477%	$59.8074	$59.81	$59.80	$59.80
Purchase #7	$23.25	11.278%	$25.8721	$25.87	$25.85	$25.90
7 purchase totals =	$673.76		$753.3754	$753.38	$753.30	$753.40