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	$106.39	5.258%	$111.984	$111.98	$112.00	$112.00
Purchase #2	$196.44	7.437%	$211.0492	$211.05	$211.05	$211.00
Purchase #3	$65.38	7.774%	$70.4626	$70.46	$70.45	$70.50
Purchase #4	$172.76	3.766%	$179.2661	$179.27	$179.25	$179.30
Purchase #5	$79.51	13.256%	$90.0498	$90.05	$90.05	$90.00
Purchase #6	$97.42	7.649%	$104.8717	$104.87	$104.85	$104.90
Purchase #7	$145.25	5.169%	$152.758	$152.76	$152.75	$152.80
7 purchase totals =	$863.15		$920.4414	$920.44	$920.40	$920.50