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	$49.60	7.649%	$53.3939	$53.39	$53.40	$53.40
Purchase #2	$128.84	10.847%	$142.8153	$142.82	$142.80	$142.80
Purchase #3	$90.40	4.242%	$94.2348	$94.23	$94.25	$94.20
Purchase #4	$166.98	4.250%	$174.0767	$174.08	$174.10	$174.10
Purchase #5	$219.94	9.224%	$240.2273	$240.23	$240.25	$240.20
Purchase #6	$82.87	3.491%	$85.763	$85.76	$85.75	$85.80
Purchase #7	$145.41	6.552%	$154.9373	$154.94	$154.95	$154.90
7 purchase totals =	$884.04		$945.4483	$945.45	$945.50	$945.40