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	$224.33	9.556%	$245.767	$245.77	$245.75	$245.80
Purchase #2	$233.29	12.182%	$261.7094	$261.71	$261.70	$261.70
Purchase #3	$242.27	4.657%	$253.5525	$253.55	$253.55	$253.60
Purchase #4	$39.33	9.693%	$43.1423	$43.14	$43.15	$43.10
Purchase #5	$64.52	6.710%	$68.8493	$68.85	$68.85	$68.80
Purchase #6	$204.46	5.803%	$216.3248	$216.32	$216.30	$216.30
Purchase #7	$100.83	10.566%	$111.4837	$111.48	$111.50	$111.50
7 purchase totals =	$1,109.03		$1,200.8290	$1,200.82	$1,200.80	$1,200.80