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	$226.71	11.734%	$253.3122	$253.31	$253.30	$253.30
Purchase #2	$61.78	9.459%	$67.6238	$67.62	$67.60	$67.60
Purchase #3	$117.97	4.340%	$123.0899	$123.09	$123.10	$123.10
Purchase #4	$181.78	11.647%	$202.9519	$202.95	$202.95	$203.00
Purchase #5	$94.33	10.196%	$103.9479	$103.95	$103.95	$103.90
Purchase #6	$50.96	6.788%	$54.4192	$54.42	$54.40	$54.40
Purchase #7	$142.75	11.311%	$158.8965	$158.90	$158.90	$158.90
7 purchase totals =	$876.28		$964.2414	$964.24	$964.20	$964.20