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	$99.40	13.271%	$112.5914	$112.59	$112.60	$112.60
Purchase #2	$186.78	8.687%	$203.0056	$203.01	$203.00	$203.00
Purchase #3	$86.46	10.363%	$95.4198	$95.42	$95.40	$95.40
Purchase #4	$209.31	7.623%	$225.2657	$225.27	$225.25	$225.30
Purchase #5	$63.76	3.295%	$65.8609	$65.86	$65.85	$65.90
Purchase #6	$77.49	6.111%	$82.2254	$82.23	$82.25	$82.20
Purchase #7	$163.58	10.693%	$181.0716	$181.07	$181.05	$181.10
7 purchase totals =	$886.78		$965.4404	$965.45	$965.40	$965.50