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	$195.59	10.860%	$216.8311	$216.83	$216.85	$216.80
Purchase #2	$57.32	3.746%	$59.4672	$59.47	$59.45	$59.50
Purchase #3	$77.28	8.444%	$83.8055	$83.81	$83.80	$83.80
Purchase #4	$101.61	9.332%	$111.0922	$111.09	$111.10	$111.10
Purchase #5	$112.93	13.102%	$127.7261	$127.73	$127.75	$127.70
Purchase #6	$105.98	9.299%	$115.8351	$115.84	$115.85	$115.80
Purchase #7	$224.29	5.146%	$235.832	$235.83	$235.85	$235.80
7 purchase totals =	$875.00		$950.5892	$950.60	$950.65	$950.50