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	$108.36	10.798%	$120.0607	$120.06	$120.05	$120.10
Purchase #2	$233.47	7.616%	$251.2511	$251.25	$251.25	$251.30
Purchase #3	$220.88	6.630%	$235.5243	$235.52	$235.50	$235.50
Purchase #4	$53.81	10.741%	$59.5897	$59.59	$59.60	$59.60
Purchase #5	$99.96	6.377%	$106.3344	$106.33	$106.35	$106.30
Purchase #6	$123.39	11.653%	$137.7686	$137.77	$137.75	$137.80
Purchase #7	$202.53	11.525%	$225.8716	$225.87	$225.85	$225.90
7 purchase totals =	$1,042.40		$1,136.4004	$1,136.39	$1,136.35	$1,136.50